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Dilated Pupils & Pupil Dilation: Causes & Symptoms

Dilated pupils are pupils that are larger than normal. They are sometimes called dilated eyes. The size of your pupils is controlled by tiny muscles in the colored part of your eye and the amount of light reaching your eyes. In bright light, your pupils constrict (get smaller) to prevent too much light from entering your eyes. In dim lighting, your pupils dilate (get larger) to allow more light in.

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Woman with black hair and blue eyes with dilated pupils.

Dilated pupils are pupils that are larger than normal. They are sometimes called dilated eyes.

The size of your pupils is controlled by tiny muscles in the colored part of your eye (iris) and the amount of light reaching your eyes.

In bright light, your pupils constrict (get smaller) to prevent too much light from entering your eyes. In dim lighting, your pupils dilate (get larger) to allow more light in.

Normal pupil size generally ranges from 2.0 to 4.0 millimeters (mm) in bright light, and 4.0 to 8.0 mm in the dark. To some degree, pupil size tends to get smaller with age.

In one study of 500 Americans ages 18 to 34 years, average pupil sizes in three different lighting conditions were found to be:

dilated-pupils-330x366_1.25x.jpg?fm=jpg&q=80
  • 3.35 mm in direct light

  • 3.86 mm in normal room lighting

  • 6.41 mm in near-total darkness

If your pupils are significantly larger than these averages, you have dilated pupils.

A dilated pupil can sometimes still react to light — that is, get smaller in bright light or when a light is shined at the eye. But typically, dilated eyes don’t respond normally to light.

A large pupil that is completely unresponsive to light is called a "fixed" dilated pupil.

Dilated pupils aren't the same as anisocoria, a common condition where both pupils react normally to light but differ in size by about a half-millimeter or more. Anisocoria is benign and affects about 20% of the population.

SEE RELATED: Small pupils: What do they mean?

What causes dilated pupils?

The most common dilated pupil causes include:

Medications

The following prescription and non-prescription medicines can cause your pupils to dilate and affect their ability to react to light:

  • Antihistamines

  • Decongestants

  • Tricyclic antidepressants

  • Motion sickness medicines

  • Anti-nausea medicines

  • Anti-seizure drugs

  • Medications for Parkinson's disease

  • Botox and other medications containing botulinum toxin

  • Atropine (used for myopia control and other medical purposes)

Eye injury

A serious, penetrating eye injury can damage your iris and cause the pupil to become dilated and irregular in shape. Sometimes, this sort of injury can occur during an eye surgery, such as a complicated cataract surgery or a corneal transplant.

Brain injury or disease

A head injury, stroke or brain tumor can affect how your pupils react to light and cause dilated pupils. One or both eyes may be affected.

This is why you see physicians checking an athlete's pupils with a penlight following head trauma sustained during sporting events, or when a patient arrives at a hospital emergency department with other possible stroke symptoms.

Recreational drug use

Research has shown that alcohol and marijuana — separately or in combination — can reduce your eyes' ability to recover from exposure to a bright light source (such as oncoming headlights at night) and adapt to changing light conditions. This effect can last two hours or longer after drug ingestion.

However, the substances themselves do not cause your pupils to dilate.

A number of illegal drugs, however, do directly cause dilated pupils. This slows your eyes' ability to react to light.

These drugs include:

  • Amphetamines

  • Cocaine

  • LSD

  • MDMA (Ecstasy)

Benign episodic unilateral mydriasis

This is an unusual but harmless condition where a person experiences sporadic episodes of one pupil suddenly becoming dilated, often accompanied by blurry vision, headache and eye pain.

Young women who are prone to migraine appear to have the highest risk of benign episodic unilateral mydriasis. In one study, the median duration of the episodes was 12 hours (some lasted much longer) and the median frequency was two to three episodes per month.

The condition resolves and the pupil returns to normal size and function without treatment.

Adie's pupil

Also called Adie's tonic pupil or tonic pupil, this is a rare neurological disorder where one pupil is larger than normal and is slow to react to light. Sometimes, the pupil does not constrict at all.

This pupil abnormality may be accompanied by poor or absent tendon reflexes. When this occurs, the condition is called Adie's syndrome.

Generally, the cause of Adie's tonic pupil is unknown; but in some cases, it may be associated with trauma, surgery, poor blood circulation or infection. There's no cure for Adie's pupil or Adie's syndrome.

Congenital aniridia

This is a rare condition where a person is born with a partially or completely absent iris, resulting in a very large "pupil." Aniridia usually affects both eyes and is accompanied by other serious eye problems such as congenital cataracts, glaucoma, incomplete development of the retina and optic nerve, nystagmus, and decreased visual acuity.

Because there is little or no iris to regulate the amount of light entering the eye, people with aniridia are very sensitive to light.

Sexual attraction

It's true — researchers have found that pupil dilation appears to correspond to adult men and women's sexual interest in other adults. But there's a catch.

One recent study showed that the pupils of male subjects dilated when they viewed images of women they found sexually attractive, whereas the pupils of female subjects typically dilated in response to images of attractive men and women alike. The study authors concluded the reason for this is unclear and that further research is warranted.

Treatment for dilated pupils

If you or someone else notices you have dilated pupils or one of your pupils looks larger than the other after head trauma, seek medical attention immediately.

The same is true if you experience sudden dizziness, headache, confusion, balance problems or other symptoms of a possible stroke.

If you notice dilated pupils after you've started taking one of the medications noted above, call your prescribing doctor for advice.

In cases other than those described above, call your eye doctor immediately for advice if you notice your pupils are dilated — especially if it comes on suddenly.

If you have dilated pupils or your pupils react slower than normal to changing light conditions, you will be more sensitive to sunlight. Eyeglasses that darken automatically in daylight or sunglasses with polarized lenses can make your eyes feel more comfortable outdoors.

Custom prosthetic contact lenses can also help reduce light sensitivity caused by dilated eyes. These lenses give the appearance of having equal pupils of normal size. Prosthetic contacts are especially beneficial for cases of aniridia and large, irregular pupils caused by trauma.

READ NEXT: What is a blown pupil?

Page published in February 2019

Page updated in November 2021

Why Are My Pupils Dilated? 5 Causes of Dilated Pupils ...

Muscles in the colored part of your eye, called the iris, control your pupil size. Your pupils get bigger or smaller, depending on the amount of light around you. In low light, your pupils open up...

You look in the mirror and notice that the dark circles in the middle of your eyes are bigger than usual. What's going on? Those dark circles are your pupils, the openings that let light enter your eye so you can see.

Muscles in the colored part of your eye, called the iris, control your pupil size. Your pupils get bigger or smaller, depending on the amount of light around you. In low light, your pupils open up, or dilate, to let in more light. When it’s bright, they get smaller, or constrict, to let in less light.

woman with dilated pupilsSometimes your pupils can dilate without any change in the light. The medical term for it is mydriasis. Medicines, injuries, and diseases can all cause this eye condition.

A few medicines can affect the muscles that control your pupils and prevent them from getting smaller when light shines in. These meds include:

  • Atropine (Atropen), which treats problems with heart rhythm, stomach issues, and some types of poisoning
  • Antihistamines, like diphenhydramine (Benadryl, Genahist, Naramin, Sominex, Unisom)
  • Decongestants, like pseudoephedrine (Afrinol, Sudafed)
  • Motion sickness and anti-nausea medicines such as dimenhydrinate (Dramamine) or a scopolamine patch
  • Parkinson's medications such as amantadine (Symmetrel) and carbidopa-levodopa (Sinemet)
  • Tricyclic antidepressants like amitriptyline (Elavil) and desipramine (Norpramin)
  • Botulinum toxin (Botox, Myobloc)
  • Anti-seizure drugs, such as phenobarbital (Luminal) and topiramate (Topamax)

Dilated pupils are one sign that someone has used illegal drugs, such as:

  • Cocaine
  • Amphetamines
  • LSD
  • Ecstasy

These drugs affect the muscle that widens the pupil, slowing how it reacts to light. So even in a bright room, the eyes stay dilated. Withdrawal from these drugs can also make the pupils stay open wide.

Pressure that builds inside your brain after a head injury, stroke, or tumor can damage the muscles in your iris that normally make your pupils open and close. One or both of your pupils can become fixed in the dilated position and can’t react to light. If that happens, you should see a doctor right away.

If you've had a head injury, your doctor or nurse might shine a light into your eye during the exam to see if your pupils get smaller.

An eye injury can damage nerves or the muscles in your iris that control your pupil size. That can also happen after eye surgery, such as cataract removal or corneal transplant.

This condition means only one pupil is dilated. It's called "benign" because it's not related to any serious conditions, but it can sometimes affect young women who get migraines. The pupil usually goes back to normal size within a few hours, but it can last for several days. You should still see your doctor to rule out anything serious. 

See your doctor or eye specialist for an exam if your pupils are enlarged and they don't get smaller in bright light. Get emergency help if you've had a head injury and your pupils look larger -- especially if one pupil is bigger than the other.

The doctor will examine your eyes. You might also have imaging tests such as computed tomography (CT) or magnetic resonance imaging (MRI) scans to look for an injury or other problems in your brain.

If a medicine caused your pupils to dilate, they should go back to normal once the drug wears off. Try to avoid the drug in the future, if you can. If you need the medication for a health problem, ask your doctor if there’s a different drug you can try that won’t affect your eyes.

While your eyes are dilated, they will be more sensitive to light than usual. Try to avoid bright places. Wear sunglasses when you go outside. Sometimes dilated pupils can affect your vision. Ask your eye doctor if you need to avoid driving until your pupils go back to their normal size.

What does it mean when one pupil dilates and the other ...

10-12-2012 · The condition of one pupil being larger than the other without having received dilating drops is called anisocoria. The causes of this are too numerous to discuss in detail. Most common is simple anisocoria, which is usually a small difference between the pupil sizes and is a normal variant. If this is a new observation then the ophthalmologist would have to determine if the abnormal pupil is ...

10-12-2012


  • Question:

    What does it mean when one pupil dilates and the other does not?


    Answer:

    There isn't enough information to answer with any specificity as more details are required.

    In the case where one pupil does not respond to dilating drops there are several possibilities. The iris could be partially stuck to the lens because of prior inflammation or trauma or prior surgery.

    The condition of one pupil being larger than the other without having received dilating drops is called anisocoria. The causes of this are too numerous to discuss in detail. Most common is simple anisocoria, which is usually a small difference between the pupil sizes and is a normal variant. If this is a new observation then the ophthalmologist would have to determine if the abnormal pupil is the smaller one or the larger one.

    A unilaterally constricted pupil can be caused by local ocular factors such as inflammation or trauma but also may be related to a failure of the dilator muscle due to a neurological condition such as Horner's syndrome. Horner's syndrome can be a benign condition or be caused by a vast array of things such as a tumor in the chest, carotid artery dissection, migraines, trauma and some medications to name just a few. It can also be congenital. Some drops and some systemic medications and drugs may cause a constricted pupil.

    A unilaterally dilated pupil can be a benign finding such as a tonic pupil. It can be related to local factors such as a history of eye trauma or surgery. It can also be a result of paralysis of the iris constrictor muscle which may result from many neurological conditions but especially from involvement of the third nerve. If that is the case this can be an emergency resulting from a brain aneurysm. There are also many drugs and systemic medications that can cause a dilated pupil. The main point here is that differences in pupil size, reactivity, or reaction, while often benign, may be a harbinger of a very serious condition or even an emergent life threatening condition. Examination by an ophthalmologist is required.



People also ask
  • How do you get rid of dilated eyes?

    To reduce the side effects of eye dilation, take the following steps:Take the rest of the day off work or school so you can rest your eyes.Keep your home darkened until the dilation wears off.Wear sunglasses when you are outside.Avoid driving until all the blurriness resolves.
    1. 1

      Imagine a dark room. Research in 2014 showed that people can sometimes dilate their pupils by imagining dark shapes or dark scenes.[1] Think of those black bears assaulting a black campground at midnight, and your eyes may widen temporarily.

    2. 2

      Focus on distant objects, or unfocus your eyes. Your pupils will get bigger as your eyes adjust to a further viewing distance.[2] Another way to approach this is to suddenly unfocus your eyes, blurring your vision as much as you can. If you're doing this correctly, your eyes will feel very relaxed; if you start to see double, you've probably crossed your eyes and need to start over.

      • With these techniques, you won't be able to observe your own eyes, so you'll need to record yourself or have a friend watch.

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    3. 3

      Face a darker part of the room. As you probably know, pupils grow to let in more light. If you aren't able to dim the surrounding lighting, you can still dilate your pupils by turning to face away from windows and light source.

    4. 4

      Try tensing your stomach. Suck your stomach in and keep the muscles tight as you watch yourself in a mirror, to see whether your pupils increase. Some people can dilate their pupils in this way, although the underlying mechanism is unidentified. If you see no change after repeated tensing and bending, move on to a different technique.

    5. 5

      Picture something that gives you an adrenaline rush. Your pupils can dilate dramatically when you are excited, or especially when sexually stimulated, due to the release of oxytocin and adrenaline. In addition to dilated pupils, these chemicals also causes your mind to race, muscles to tense up, and breathing to go faster. Through biofeedback, people can learn to "drive" their adrenaline levels up or down.[3]

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    1. 1

      Use allergy eye drops. Pick up some over-the-counter eye drops intended to be used to treat allergies. These can cause your eyes to become dilated. Be sure to read the instructions, and never use more drops than the label recommends.

    2. 2

      Drink an espresso or take decongestants. Stimulants that work on the sympathetic nervous system can trigger your iris muscles to dilate your pupils. These include caffeine, ephedrine, pseudoephedrine, and phenylephrine. The last three are found in most over-the-counter decongestants.

    3. 3

      Consider 5-HTP supplements. This is an over-the-counter drug you can find at pharmacies or anywhere that sells health supplements. While 5-HTP is generally safe, too high a dosage can cause dangerous effects from "serotonin syndrome."[4] Stick within the recommended dosage, and avoid 5-HTP entirely if you are on LSD, cocaine, antidepressants, large B-vitamin doses, or other substances that increase serotonin levels.[5]

    4. 4

      Avoid other substances unless recommended by a doctor. Some prescription eye drops can dilate pupils, but have serious side effects that should be weighed by a doctor. If you are going through methadone treatment or have a medical condition that constricts your pupils, ask your doctor for advice on how to counteract this.

      • Some recreational drugs cause dilated pupils as well. These are illegal in most areas, and can come with additional health risks if combined with other substances that cause dilated or constricted pupils.

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    1. 1

      Look at a bright, natural light. Stare at a bright window for a couple seconds. This will cause your pupils to shrink immediately. If you're outside, step into a patch of sunlight, rather than staying in the shadows.

      • While light bulbs will work as well, natural light is more effective.
      • Never look directly at the sun, as this could damage your eyes.
    2. 2

      Focus intently on something close to you. Your pupils will narrow as you change your focus to something in front of your face. You can start by closing one eye and placing your finger in front of the open one. With practice, you can learn to focus your eyes close even when there's nothing there.

    3. 3

      Consider medication. There are a variety of medications used to constrict the pupil, but these are usually only available as a prescription, or even administered by the doctor only.

      • Opiates constrict pupils, but most examples are illegal in most countries. They can also cause serious harm, especially when combined with other drugs that cause pupil constriction or dilation.

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    Add New Question
    • Question

      How does the pupil dilate and constrict?

      wikiHow Staff Editor

      wikiHow Staff Editor
      Staff Answer
      This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

      wikiHow Staff Editor

      There are two sheets of circular muscles in the iris, one that expands to dilate the pupil in low light and one that contracts to constrict it in bright light.

    • Question

      What can make your pupils big?

      wikiHow Staff Editor

      wikiHow Staff Editor
      Staff Answer
      This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

      wikiHow Staff Editor

      The most common reason is that the lighting is dark or dimly lit, but there are other reasons why your pupils might dilate. There are certain prescription drugs, such as atropine, antihistamines, decongestants, tricyclic antidepressants, botox, and certain anti-seizure drugs that can cause this. Many illegal drugs are also known to cause dilated pupils, including, cocaine, amphetamines, psychedelics and ecstasy. Sometimes a head injury, a stroke or another brain disorder can cause pupils to dilate as well as certain injuries to the eye itself. Sometimes pupils can dilate for no specific reason, even for several days, but not be dangerous or indicate a more serious condition (known as benign episodic unilateral mydriasis).

    • Question

      I am newly taking Naltrexone, and it has made my pupils big. The people around me think I am on drugs. What can I do?

      Community Answer

      Explain to them that you are on a medicine that has that side effect.

    • Question

      How do I know if I have perfect eye control?

      Community Answer

      Test it out by looking in a mirror as you try to change them.

    • Question

      Are dilated pupils easily noticed?

      HaniyaTheNerd

      It depends on eye color. If the iris is brown, especially very dark brown, it won’t be that noticeable. If the iris is a lighter color, then people may notice it. If you wear color contacts, no one will notice.

    • Question

      How do I only dilate one pupil?

      Community Answer

      Unless you have perfect eye control, this is impossible.

    • Question

      Can this make you have bad eyesight?

      Community Answer

      Yes, it can definitely harm your vision. A lot of these techniques, if done repeatedly, put a lot of strain on your eyes and can hurt your eyesight over time.

    • Question

      Is doing this bad for your eyes?

      Community Answer

      Yes.

    • Question

      Will erythromycin eye drops help to dilate or shrink my pupils on command?

      Community Answer

      No-––antibiotic drops do not penetrate deeply enough through the protective layers of the eye to affect pupillary functions.

    • Question

      Will crying help constrict pupils?

      CheeShay

      That depends. If you're in a dark then yes, and if you're in a bright room then no. That's a tricky question because it really depends on what it looks like around you.

    Ask a Question


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    Co-authors: 66

    Updated: January 1, 2021

    Views: 2,295,242

    Categories: Featured Articles | Eye Tricks

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    How to Get Rid of Puffy Eyes Fast: 5 Home Remedies & How They Work
  • Why do I Hate getting my eyes dilated?

    Your vision will be blurred and more sensitive to blinding light from the dilating eye drops, so driving is one of the things you should avoid. Besides putting other drivers and yourself at risk, you can also risk causing permanent damage to your retinas from UV exposure.

    By Stephanie Langmaid

    Medically Reviewed by Whitney Seltman, OD on March 16, 2021

    Dilation is part of a thorough eye exam. You may think it’s a hassle. But it gives your doctor a good look inside your eye. It’s especially important if you’re having eye pain or vision problems, or if you’re more likely to get certain eye diseases.

    Normally, your pupil gets smaller when light shines into it. In dilation, your doctor uses special eye drops to force the pupil to stay open. This allows them to see much more of the back of your eye, including the entire retina, the part of the retina called the macula, and the optic nerve.

    During a dilated exam, your doctor can spot problems like a torn or detached retina or an eye tumor. They can also diagnose and monitor common eye diseases that can take away your sight:

    • Diabetic retinopathy: Signs include blood vessels that leak, swell, or grow abnormally in the retina.
    • Glaucoma: Your doctor looks for damage to the optic nerve.
    • Age-related macular degeneration: Protein or pigment buildup and unusual growth of blood vessels are symptoms of a breakdown of the macula.
    • Cataract: A clouding of your natural lens.

    Almost all of these conditions are painless, so you may not even know you have one unless you see your doctor and have your eyes dilated.  

    Everyone’s eyes react differently to the dilation drops. It usually takes 15 to 30 minutes for your pupils to open completely. Most people are back to normal within about 4 to 6 hours. But for you, the effects could wear off more quickly, or they could last much longer.

    Dilation doesn’t typically affect your distance vision, unless you are farsighted and don’t have glasses to correct your vision. But because your pupils can’t control the amount of light going into your eyes, the glare outside may bother you. For some people, that makes it unsafe to drive.

    If you’ve never had your eyes dilated, get someone else to drive you home from your appointment. Once you’ve had it done, you’ll know whether dilation means you can’t drive after an exam.

    Whether or not you get behind the wheel, it’s a good idea to bring sunglasses with you so you can shield your eyes after the exam.

    Dilating drops make it hard for your eyes to focus on things close to you. You probably won’t be able to read, use the computer, or do other tasks that require near vision after your appointment, unless you wear bifocals or use reading glasses. If you work outside, the bright light may bother you. It may be easier to make an appointment later in the day so you don’t have to go back to work.

    The National Eye Institute recommends everyone over 60 have a dilated exam once a year. If you’re African-American, you’re at higher risk for glaucoma, so the yearly recommendation starts at age 40. If you have diabetes, you should also have a dilated exam once a year no matter how old you are.

    Dilation is often a normal part of an eye exam for people who wear glasses or contacts. But if you’re young and your eyes are healthy, you may not need it every time. Your doctor also may be able to use other methods to check your retina without dilating your eyes, but they may not work as well. See what your doctor recommends.

    Many eye diseases are more common as you get older. The American Academy of Ophthalmology says everyone should get a baseline exam with dilation when they’re 40. That way, your doctor can track any changes that could signal a problem.

    © 2021 WebMD, LLC. All rights reserved. View privacy policy and trust info

    Why Do I Need to Get My Eyes Dilated?
  • What to expect when your eyes are dilated?

  • Why one of Your Eyes is smaller than the other?

    The asymmetric pupil size makes one eye look smaller than the other. The difference between pupil size ranges from 0.5 to 1 mm. Anisocoria starts at birth and might be caused by a disorder of blood vessels, brain, eyes, or nerves. This condition can also temporarily happen to people with symmetric pupils.

    It is not uncommon to meet an individual whose one eye is bigger than the other. This occurrence can be caused by many different things, the most common of which will be discussed in this article, along with suggestions to help improve asymmetric eyes.

    One Eye Is Bigger Than Other, Why?

    There are numerous instances which can cause one's eyes to be misshapen, leading you to have one eye bigger than the other. Such instances include:

    1. Natural Asymmetry

    It is quite common for one's eyes to be somewhat different in size and shape, causing them to appear asymmetrical. In many cases, one eye will be narrower than the other, while the other looks more rounded. In such condition, there is no cause for concern, as it is entirely normal. If you notice that your eyes appear asymmetrical when you are dehydrated or tired, it may be caused by these things, meaning getting plenty of rest and drinking plenty of fluids may prove beneficial.

    What to do:If you wish to have more symmetrical looking eyes, then there are a few simple techniques one can employ using makeup.

    • Try using a pale/golden color-based shadow around your eyes, then using highlighter to lightly smudge toward the corner of the eye.
    • Use eyeliner on the eye which is smaller, to make it appear thicker and fuller.
    • There are also numerous mascaras available on the market which work to lengthen one's lashes, doing this on one's smaller eye will help it look bigger, especially when used with an eyelash curler.

    2. Droopy Eyelid

    A droopy eyelid, or ptosis, can happen naturally in individuals, or be caused by other instances such as migraines, nerve issues, an eye infection, an allergic reaction, or certain conditions (such as the autoimmune condition known medically as myasthenia gravis). A droopy eyelid may also be caused by aging, and it can also be present at birth. Whatever the cause, a droopy eyelid can cause you to have one eye bigger than other.

    What to do: One should only feel the need to take action in regards to their drooping eyelid if it is causing impairment in vision, getting worse progressively, or is coinciding with other symptoms. In such cases, medical help should be sought out from a health care professional.

    3. Anisocoria

    One's pupils may show a slight variation in size from birth, ranging from around 0.5 to 1 mm difference in pupil size, the same variation may also occur in individuals who have symmetric pupils, which is known as anisocoria, which may be caused by a disorder to the eyes, nerves, brain, or blood vessels.

    What to do: One should not worry if one pupil becomes slightly bigger than another without other symptoms. In many cases, the difference in pupil size will only be temporary. That being said, one should seek emergency medical help if other symptoms are present, such as vision changes, headache, fever, nausea, vomiting, or if it happens after an injury to one's head.

    4. Amblyopia

    This condition happens when an individual is in early childhood, caused by atypical development of one's vision at that period. Amblyopia causes one or both eyes to move inward or outward without consciousness, making it appear as though they are not working in synchronicity with each other, leading to impaired vision and one eye bigger than other.

    What to do: As this condition can cause serious problems if progressing, such as severe loss of vision, one should take their child to visit an ophthalmologist if they notice the children's eyes to be "lazy" or wandering.

    5. Exophthalmos

    When an individual's eyes bulge (which can occur in one or both eye), it is known as exophthalmos. This is often caused by certain medical conditions, such as a hyperactive thyroid, or a tumor growing behind one's eye/eyes. As this condition is slow to progress, it can be hard to notice, one may only see the change when looking at old photographs.

    What to do: If one was to have one eye bigger than other because the eye appeared to be bulging, then one must consult a medical professional as soon as possible to check for serious underlying conditions that may be causing such an instance.

    6. Strabismus

    Strabismus, or crossed eyes, is quite common in babies, and can also occur in adults. The conditions makes one is unable to simultaneously align one's eyes; each eye may turn outward, inward, upward, or downward independently. This condition can be consistent or intermittent, and can cause other symptoms including double vision and decreased/impaired vision.

    What to do: There are numerous things one can try to ease the symptoms of strabismus. One may wish to wear an eye-patch over one of their eyes, use eye drops, carry out visual exercises, or try wearing glasses. In some cases, one may require surgery to properly correct the condition.

    7. Grave's Disease

    An overactive thyroid can cause one to develop grave's disease, which can cause swelling of the eyes, as well as soreness, watering, a gritty feeling, and redness. This condition can make it seem as though you have one eye bigger than other, due to the swelling.

    What to do: One should seek medical assistance to treat an overactive thyroid.Bulging eyes may be helped with eye drops, the use of eye ointments and eye pads at nighttime. 

    Why Is One of Your Eyes Smaller Than the Other?
One Pupil Bigger Than the Other, Why, Causes of Dilated ...

18-07-2017 · What causes one pupil to be bigger than the other? Is it stress, anxiety, or…

18-07-2017

What causes one pupil to be bigger than the other? Is it stress, anxiety, or headaches? Unevenly dilated pupils are referred to as anisocoria. They can make you look imbalanced, worried or even scary. What can you do about unequal pupils?

Pupils are the black center parts of your eyes, which become dilated (large) when in dim light, and constricted (smaller) when in bright light. Normally, both pupils should be of the same size, and should have the same response to light exposure. But, when you have unequal pupils, they are known as anisocoria.

One pupil bigger than the other anisocoria

One pupil bigger than the other – anisocoria
pictures, illustration.

If the sizes of your pupils are very unequal, there is a chance that you will notice this discrepancy. In many cases, unequal pupils are only noticed during an eye examination by a doctor. The unequal pupils will by themselves not cause any symptoms, even though you may occasionally experience a problem focusing on objects that are very close to you.

Additionally, the underlying disorder for anisocoria may at times cause more symptoms e.g.

  1. Redness and eye pain
  2. Drooping eyelids
  3. Loss of vision
  4. Headaches
  5. Double vision

Many people seek medical attention because of these more noticeable symptoms, rather than because of having one pupil bigger than the other. Read on to find out what causes one pupil bigger than the other, available treatment options, and whether it is possible to prevent it.

What is Anisocoria (Dilated or unequal pupils)?

Aniscoria from anxiety or injury

Aniscoria from anxiety or injury.

Typically, the size of your pupils should be similar in each eye, and both eyes should constrict or dilate together. Anisocoria is a term used to refer to pupils that are of different sizes at any one time. Anisocoria can be because of an underlying medical condition or could be physiologic (normal).

According to HealthLine, approximately twenty percent of the world’s population has anisocoria. But, the amount present may vary from one day to the next, and it could also switch between your eyes. If anisocoria is not associated with or is not because of a medical condition is referred to as physiologic anisocoria. Normally, when it comes to physiologic anisocoria, the existing difference between the size of the pupils in both eyes will not exceed one millimeter.

Symptoms

According to WebMD, many people do not realize that their pupils are of different sizes until an eye exam is carried out. But, if anisocoria was to develop due to a problem with your eyes, you would likely notice symptoms such as:

  1. Fever
  2. Headaches
  3. Reduced sweating
  4. Drooping eyelids
  5. Problems when attempting to move your eyes
  6. Eye pain

Why is one pupil bigger than the other? Causes

The most common causes of one pupil being larger than the other include:

1. Dilated pupil

In a case where one pupil refuses to make a response to the dilating drops, there could be a number of possibilities. Your iris may be partially stuck to your lens due to prior surgery, trauma, or inflammation. A singly constricted pupil may be caused by ocular issues e.g. trauma or inflammation, but, it can also be related to the failure of your dilator muscle because of the presence of neurological conditions e.g. Horner’s syndrome.

This syndrome may be a benign condition, or it may be caused by a wide variety of issues e.g.

  1. Presence of a tumor in your chest
  2. Migraines
  3. Use of certain medications
  4. Carotid artery dissection

Additionally, the syndrome may also be congenital. There are certain medications and drops, which have been known to cause constricted pupils.

See also:

2. Concussion and unequal pupils

Sustaining blunt force trauma to the head is one of the primary causes of temporary anisocoria, which may occur due to:

  1. Sports related injuries e.g. rugby or American football
  2. Accidents e.g. automobile accidents
  3. Other violent events

A brain concussion can cause unequal pupils, more so if the injury you have sustains get to affect certain parts of your brain. In addition, if your skull comes to an abrupt stop, your brain may not only be injured in the side that has been impacted by the stop, but it may also end-up being damaged on the opposite side as it is bouncing back. It is also possible for your eye to be injured in a similar manner during the movement of your vitreous body.

Concussions are deemed to be dangerous by doctors, as they can cause brain tissue damage as well as associated swelling. Most people assume that black eyes are relatively minor. However, any person who has sustained an injury to the face or eye resulting in the black eye should be evaluated by an emergency physician through the use of CAT scans or X-rays in a bid to monitor the voluntary movements of the eyes, as well as rule out the possibility of any damage to the surrounding eye orbits and bones.

The bones found in this area are quite thin and can be broken very easily. As such, a blow to your eye could push your eyeball back into the space that is available behind it, which would result in the compression of the muscle tissue, and the fat filling this orbit. This would then make the fragile bones in the orbit to become fractured.

3. Anxiety and dilated pupils

Dilated pupils are likely to occur with any kind of anxiety, even though they are most common during the periods of deep anxiety, which can occur under the following conditions:

  • Phobias
  • Panic attacks/panic disorders
  • PTSD

But, you should note that the dilated pupils can occur during any severe anxiety sessions. Typically, when the flight or fight response is functioning in a proper manner, it should only become activated during periods when you have intense fear e.g. times when you may need to fight or start running away. In such instances, your body will need to have great vision. It is the reason why your pupils start to dilate. When the pupils become dilated, the eyes start to let in more light, which means that your vision will temporarily become improved.

Is it possible to reduce pupil constriction?

Unlike all the other symptoms associated with anxiety attacks, you cannot be able to control pupil dilation. It is not possible to “talk your eyes down” to prevent dilation, and there are no exercises that you can conduct to prevent their dilation.

Your pupils form a part of your body that is 100% automatic, and therefore, when they change in size, you have no option but to wait for them to return to normal on their own. Controlling your anxiety is the only available treatment for pupil dilation.

If you constantly find that your pupils are dilated when dealing with an anxiety attack, the good news is that there are many techniques that you can use to effectively control your anxiety related symptoms.

4. Headaches

One pupil bigger than the other accompanied by headaches is often associated with Horner’s syndrome. In Horner’s syndrome, the headaches are said to be excruciating, unilateral, and highly throbbing, which can come at varied times.

On occurrence, they may refuse to subside, even when you attempt to avoid noise or light, or even have some rest. In addition to the throbbing headaches, your eyes could also become droopy and sunken. If you notice this, it is recommended that you visit your ophthalmologist for evaluation purposes.

5. Damage to your iris sphincter

Trauma can make your iris sphincter to become inflamed or affected. Your pupil has an irregular shape, and magnification will show that your iris muscles have become damaged.

6. Horner’s syndrome

This is a very rare disease, which comes about when specific nerves that travel from your eyes to your brain become damaged. Note that this is not a disease, but it is an indication that you have an underlying medical condition, which may include:

One pupil bigger than the other dilated

Unequal pupils from anxiety.

  • Stroke
  • Tumor
  • Spinal cord injury

There may be instances where the causative factors are not known. In such cases, Horner’s syndrome will only affect one side of your face. Symptoms of the Horner’s syndrome include:

  1. Decreased pupil size
  2. Decreased sweating on one part of your face
  3. Presence of a loose eyelid

When these happens, the pupil that is affected will become smaller, and it may start reacting abnormally to changing light conditions.

7. Chemical blockade

Anisocoria is likely to occur in the event that Para sympatholytic chemicals come into direct contact with your Conjunctiva. It can affect the iris sphincter muscles, which would then make your pupil to expand and become very wide. It is a common occurrence among people who have been exposed to plants that contain Atropine.

8. Failure of your Parasympathetic

A breakdown of the parasympathetic will make your pupils to become dilated. Pupil dilation means that they will react very slowly to any light that they are exposed to.

In such a condition, you will need to be conscious about the third nerve palsy, which is mainly caused by aneurysm.

Diagnosis of Anisocoria

It is recommended that you contact your doctor immediately you notice one pupil bigger than the other. When you go for your appointment, the doctor will examine both eyes, and also take your vitals. At this point, ensure you discuss any other symptoms that you could have been experiencing. For instance, you need to speak out if you have any experienced any of the following recently:

  1. Eye pain
  2. Changes in your vision
  3. Light sensitivity
  4. Stiff neck
  5. Fever

Based on the symptoms described, and your existing medical history, additional tests could be ordered by your physician, to enable him/her diagnose the underlying cause of this problem.

For instance, the tests recommended could include:

  • CT scans
  • Eye exams
  • Complete blood count
  • Blood differential
  • MRI
  • X-ray
  • Spinal tap or lumbar puncture

Treatment for unequal pupils

In many cases, anisocoria will not need to be treated as it does not affect your eye health or eyesight in any way. But, if the condition is related to a problem with your eyes, then this problem will need to be addressed, in order to eliminate the one pupil bigger than the other problem.

If you happen to have an abnormal growth e.g. a brain tumor, the doctor may recommend that you undergo surgery in order to have it removed. Chemotherapy and radiation therapy are alternatives to surgery, which can also be used in removing the brain tumor.

You can manage this condition by:

  1. Attempting to determine what is causing it. Keep in mind that there are very many conditions, which could be responsible
  2. If it has been caused by medication e.g. eye drops and asthma inhalers, ensure you avoid this medication
  3. If it has been caused by trauma, your physician may prescribe some medication to assist with the inflammation

Prevention

There are certain cases of anisocoria, which are not only impossible to predict, but they cannot be prevented as well. However, there are certain steps that can be taken in order to prevent the development of uneven pupils. For instance:

  1. Make sure you wear a helmet when you are playing contact sports
  2. Always wear your seatbelt when you are driving
  3. When using heavy machinery, ensure that you wear protective gear
  4. Report any changes in your vision to your physician

It is always recommended to ensure that you seek immediate medical assistance if you notice any differences in your pupil sizes. The physician will be able to identify the underlying cause of these differences and provide you with medication to assist you restore your vision.

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Eye Dilation: A Guide (How Long It Lasts, Side Effects ...

Eye dilation works to increase the size of your pupils. Doing this allows the doctor to look at your retina and optic nerve to determine their level of health. For most people, their eyes remain dilated for four to six hours. It takes approximately 30 minutes for the pupils to dilate enough for the doctor to perform the eye examination.

Table of Contents

Eye dilation works to increase the size of your pupils. Doing this allows the doctor to look at your retina and optic nerve to determine their level of health.

For most people, their eyes remain dilated for four to six hours. It takes approximately 30 minutes for the pupils to dilate enough for the doctor to perform the eye examination.

Everyone reacts differently to the eye drops used to dilate the eyes. While the exact timeline will vary, you generally have to wait at least a few hours for the effects to wear off.

close up of dilated pupils

The actual dilation of your eyes does not cause discomfort. But when your eyes are dilated, you may feel somewhat uncomfortable since your eyes have far less protection against light.

Your doctor will provide you with instructions on how to care for your eyes until the effects of the dilation wear off. For example, you can usually drive, but if your eyes are especially sensitive, it is best to avoid driving until the effects are gone.

What Is Eye Dilation?

During an eye examination, the doctor may dilate your eyes so they can look at the structures located at the back of your eye. They are looking for abnormalities that may indicate the following conditions:

  • High blood pressure: The retina’s blood vessels can experience damage if you have high blood pressure that goes untreated, especially long term.
  • Retinal detachment: This refers to the retina pulling away from the blood vessels that are attached to it. As a result, the retina gets insufficient nutrients and oxygen.
  • Diabetes: People with diabetes are at risk for diabetic retinopathy, especially if your high blood sugar levels are uncontrolled over the long term. This condition affects the retina’s blood vessels.
  • Macular degeneration: This condition is characterized by the macula element of the retina sustaining damage. It can result in vision loss that is irreversible.
  • Glaucoma: There are different types of glaucoma that result in damage to the optic nerve. Eye pressure getting abnormally high is the typical cause of the damage.

Eye dilation may be done as part of a comprehensive eye examination or to look for an acute injury, such as a retinal detachment. No matter the reason for the dilation, it is performed in the same manner. The doctor will input eye drops that work to widen your pupils.

How often you need to have your pupils dilated will depend on several factors. For those with relatively good overall health, your doctor may only recommend it when you have routine eye examinations. The following may impact the schedule your doctor recommends:

  • You are over 60 years old.
  • You have a history of retinal detachment or other eye issues that affect the structures at the back of your eye.
  • You are experiencing new eye symptoms.
  • You are Hispanic or African American, which means you have an increased glaucoma risk.
  • You have diabetes or other health issues that can affect your eye health.

How Does It Work?

For eye dilation, or mydriasis, your doctor inputs eye drops, and it takes 20 to 30 minutes for your pupils to achieve full dilation. If your eyes are lighter in color, they tend to dilate faster than brown eyes.

Once your pupils achieve full dilation, your doctor will examine your eyes using a magnifying lens. This allows them to better visualize your macula, retina, and optic nerve.

The average dilation lasts four to six hours. The exact eye drops the doctor uses impact how long your eyes remain dilated.

Commonly used eye drops include:

  • Phenylephrine
  • Hydroxyamphetamine
  • Atropine
  • Tropicamide
  • Cyclopentolate

The doctor usually inputs two types of drops into your eyes to dilate your pupils. One of the drops used causes the muscles that control the pupil to contract so the pupil becomes larger. Phenylephrine is an example of this type of eye drop.

The second type that is used relaxes the muscle that is responsible for the eye lens focusing. It also relaxes the muscles that allow the pupil to become smaller. Cyclopentolate is an example of this type of eye drop.

If you are having eye dilation performed for the first time, you should plan to experience dilation for at least six hours. Consider getting a ride home from the doctor, and make sure you have sunglasses to reduce the light sensitivity that is common when your pupils are dilated.

Can You Reduce Dilated Eyes Faster?

How long your eyes remain dilated depends on you and how you respond to the eye drops the doctor uses.

There is no way to r...

There is no way to reduce your pupil size faster. You might consider taking a nap once you get home to reduce how much light your eyes are exposed to.

Since it can be hard to do things like read or see a television screen if your vision is blurry, it is best to avoid these activities until the effects wear off.

Once your eyes are dilated, it is common for your vision to be blurry. If you try to focus on nearby objects, it can be difficult.

Bright lights can cause discomfort since your eyes will be very light sensitive. The eye drops the doctor uses may sting for a few seconds after they are applied.

These side effects usually go away as your pupils start to reduce in size. For most people, they are mild and do not cause intense discomfort. If any of the side effects are particularly bothersome, call your doctor.

If you wear contact lenses, your doctor will suggest that you avoid putting them in until the dilation reduces. They may recommend that you don’t wear contacts until the next day. If you wear regular eyeglasses, you should be able to put them on as soon as the doctor completes your eye dilation examination.

To reduce the side effects of eye dilation, take the following steps:

  • Take the rest of the day off work or school so you can rest your eyes.
  • Keep your home darkened until the dilation wears off.
  • Wear sunglasses when you are outside.
  • Avoid driving until all the blurriness resolves.

While rare, it is possible for the eye drops to cause an allergic reaction, such as red eyes and swelling of the eyelids. If atropine is used, the following side effects are possible:

  • Dry mouth
  • Rapid pulse
  • Fever
  • Facial flushing

Compared to other eye dilation eye drops, atropine tends to be longer acting.

drive safely

How Long After Eye Dilation Can You Drive?

If you do not experience any side effects affecting your vision, you can resume driving. It is typically recommended that you avoid driving if you experience effects, such as blurriness or trouble focusing on objects.

If it’s your first dilation eye examination, plan on getting a ride home since you don’t know how the dilation will affect you. This ensures you are prepared just in case your vision is affected enough that driving yourself home could be dangerous.

Eye Dilation as a Treatment

Dilating the eyes may benefit certain eye conditions, such as lazy eye and inflammation in the eye. When used as a treatment, the same eye drops used to dilate your eyes during an examination are used. The overall process is the same.

Dilation is usually done as part of a comprehensive eye examination. It may also be done in an acute setting to evaluate a possible injury to the eye.

Eye Dilation Costs

Most often, eye dilation is included in the total cost of a comprehensive eye exam, which averages to 0 without insurance.

If billed on its own, dilation generally costs about to .

Undilated vs. Dilated Eye Exam

In an undilated eye exam, the optometrist can check:

  • Your vision
  • Structure of the undilated pupil
  • Iris
  • Visual field
  • Eye’s drainage angle

With a dilated eye exam, the doctor can also check:

  • Back of your eye
  • Entire retina
  • Optic nerve
  • Macula

Essentially, dilation lets more light into your eye, so the doctor is better able to see the entire eye.

Eye Dilation FAQs

  • No, dilation does not cause pain. You may experience sensitivity to light and some blurriness, however.

  • It’s generally recommended as part of a comprehensive eye exam, particularly if you wear glasses or contact lenses, or if you are over 60. If you are young and have no vision issues, you may not need to have your eyes dilated at every eye exam.

  • What types of doctors do eye dilation?

    Optometrists and ophthalmologists generally dilate eyes.

  • How long does it take for eye dilation to wear off?

    Eye dilation generally lasts 4 to 6 hours. Then, the medication has usually fully worn off.

  • When can I drive after eye dilation?

    It’s recommended to wait 4 to 6 hours before driving after eye dilation.

References

Eye Dilation: Necessary With Every Eye Exam? (February 2018). Mayo Clinic.

What to Expect When Your Eyes Are Dilated. (September 2019). American Academy of Ophthalmology.

What Is a Comprehensive Dilated Eye Exam? National Eye Institute.

All About Red Caps: Mydriatics and Cycloplegics. (June 2019). Optometry Times.

Eye Dilation. Children’s Hospital of Philadelphia.

The Eyes Have It for High Blood Pressure Clues. (December 2018). American Heart Association.

What Are Dilating Eye Drops? (May 2020). American Academy of Ophthalmology.

Facts About Diabetic Eye Disease. National Eye Institute.

Dilating Eye Drops. American Association for Pediatric Ophthalmology and Strabismus.

How Much Does an Eye Exam Cost in California? (July 2021). Everything What.

The information provided on this page should not be used in place of information provided by a doctor or specialist. To learn more, read our Privacy Policy and Editorial Policy pages.

Eye dilation: Necessary with every eye exam?

Whether eye dilation during an exam is necessary depends on the reason for your exam, your age, your overall health and your risk of eye diseases. The eye drops used for dilation cause your pupils to widen, allowing in more light and giving your doctor a better view of the back of your eye. Eye dilation assists your doctor in diagnosing common ...

Is it necessary to have my eyes dilated during every eye exam?

Answer From Alaina L. Softing Hataye, O.D.

Whether eye dilation during an exam is necessary depends on the reason for your exam, your age, your overall health and your risk of eye diseases.

The eye drops used for dilation cause your pupils to widen, allowing in more light and giving your doctor a better view of the back of your eye. Eye dilation assists your doctor in diagnosing common diseases and conditions, possibly at their earliest stages. They include:

  • Diabetes
  • High blood pressure
  • Macular degeneration
  • Retinal detachment
  • Glaucoma

Eye dilation also makes your vision blurry and your eyes more light sensitive, which, for a few hours, can affect your ability to drive or work. So if eye dilation is greatly inconvenient, ask your doctor about arranging another appointment. Alternatives to dilation are available, but they aren't as effective for allowing a careful examination of the back of your eye.

In determining whether eye dilation is necessary for you, your eye doctor may consider:

  • Your age. The risk of eye diseases increases with age. The National Eye Institute recommends a dilated eye exam once every one to two years if you're 60 or older.
  • Your ethnic background. People of certain ethnic backgrounds are at increased risk of some eye diseases. Black people and Hispanics, who are at increased risk of glaucoma, are advised to have a dilated eye exam every one to two years, starting at age 40.
  • Your eye health. Having a history of eye diseases that affect the back of the eye, such as retinal detachment, may increase your risk of future eye problems.
  • Your overall health. Certain diseases, such as diabetes, increase the risk of eye disease.
  • The reason you are seeking an eye evaluation. Certain symptoms may require a dilated examination to determine the cause. Some conditions requiring follow-up examinations may not need dilation at every visit unless there are new symptoms or concerns.
Dec. 31, 2019

  1. Comprehensive adult medical eye evaluation - 2015. American Academy of Ophthalmology. https://www.aao.org/preferred-practice-pattern/comprehensive-adult-medical-eye-evaluation-2015. Accessed Jan. 5, 2018.
  2. What is a comprehensive dilated eye exam? National Eye Institute. https://www.nei.nih.gov/healthyeyes/eyeexam. Accessed Jan. 5, 2018.
  3. Aging and your eyes. National Institute on Aging. https://www.nia.nih.gov/health/aging-and-your-eyes. Accessed Jan. 5, 2018.
  4. Facts about glaucoma. National Eye Institute. https://nei.nih.gov/health/glaucoma/glaucoma_facts. Accessed Jan. 5, 2018.
  5. What to expect when your eyes are dilated. American Academy of Ophthalmology. https://www.aao.org/eye-health/drugs/what-to-expect-eyes-are-dilated. Accessed Jan. 5, 2018.
  6. Frequency of ocular examinations - 2015. American Academy of Ophthalmology. https://www.aao.org/clinical-statement/frequency-of-ocular-examinations. Accessed Jan. 11, 2018.
  7. Softing Hataye AL (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 11, 2018.
See more Expert Answers

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Cause of One Pupil Temporarily Dilated, No Response to ...

30-05-2018 · If you suddenly realize that one pupil is noticeably larger than the other and does not respond to light, take this matter seriously. It could mean a problem with your brain. The key issue here is the lack of response to light, as in, shining a flashlight into the larger pupil and observing no response.

30-05-2018

It could mean a problem with your brain.

The key issue here is the lack of response to light, as in, shining a flashlight into the larger pupil and observing no response.

Or, if you’ve been in a dim room and then flip on the lights, holding a mirror before yourself, and you see the “normal” pupil adjusting, but the other one doesn’t show much response.

This is very concerning – even if it was temporary and soon after, your pupils seem to be the same size again and are responding to changes in light.

“If you had your eyes dilated at the eye doctor’s office and one is still dilated, the dilation will go away by the next day,” says Dr. Brian Boxer Wachler, MD, eye surgeon and founder of The Boxer Wachler Vision Institute, and developer of the Holcomb C3-R® procedure which treats a degenerative eye disease.

However, when someone notices that one pupil is bigger than the other, there may be no recent history of optometrist eye drops to dilate the pupil.

Dr. Boxer Wachler explains, “Without being dilated with eye drops, if one pupil is dilated and not responsive to light, this could be from a brain tumor. You need to get it checked out immediately.”

It may also be caused by a brain aneurysm – another serious condition that needs prompt medical attention.

A brain aneurysm is a bulge in a blood vessel that may rupture, spilling blood into the brain. Shutterstock/Veronika Zakharova

There is yet a third very serious condition that can cause the appearance of one pupil larger than the other: ocular melanoma.

If the dark cancerous pigment is in the pupil, it can create the illusion that the pupil is more dilated than the other, when in fact, what the patient is seeing is the dark pigment of the cancer expanding beyond the pupillary border.

Can It Ever Be Normal for One Pupil to Be Bigger than the Other?

Yes. This is called physiologic anisocoria. It can come and go and alternate eyes.

However, there’s two things to note about this benign condition which affects an estimated 20 percent of the general population.

• The difference in pupil size is very minimal, not particularly obvious, and almost always detected by the individual himself rather than someone speaking to him.

• Both pupils respond to light normally.

• There are no other associated symptoms.

• This is a harmless phenomenon of body asymmetry, just like, for instance, one nostril might be bigger than the other.

dr. boxer wachler
Dr. Boxer Wachler has delivered hundreds of lectures on eye surgery to thousands of eye surgeons from around the world, and is a pioneer in keratoconus treatment.se of One Pupil Temporarily
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  

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Top image: Tair1978, CC BY SAp Dilated, No Response to Light, brain tumor, aneurysm
allaboutvision.com

Anisocoria is different pupil sizes in each eye. One pupil may be bigger than normal, or one pupil may be smaller than normal, resulting in unequal pupils. In most cases, anisocoria is mild, constant and no cause for concern. But if it occurs suddenly, this can be a sign of a serious medical condition and you should see an eye doctor immediately. Anisocoria is pronounced “an-eye-so-CORE-ee ...

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young boy with anisocoria

Anisocoria is different pupil sizes in each eye. One pupil may be bigger than normal, or one pupil may be smaller than normal, resulting in unequal pupils. In most cases, anisocoria is mild, constant and no cause for concern. But if it occurs suddenly, this can be a sign of a serious medical condition and you should see an eye doctor immediately.

Anisocoria is pronounced “an-eye-so-CORE-ee-ah”.

Anisocoria types and causes

There are four main types of anisocoria:

  1. Simple anisocoria

  2. Pathologic anisocoria

  3. Mechanical anisocoria

  4. Pharmacologic anisocoria

Simple anisocoria

Simple anisocoria — also called essential anisocoria or physiologic anisocoria — is the most common type of anisocoria. It’s a benign (harmless) condition that affects approximately 20% of the population. 

In simple anisocoria, the difference in pupil size is usually 1 millimeter (mm) or less, and both pupils react normally to light. The presence of simple anisocoria does not appear to be influenced by sex, age or eye color. 

The exact cause of simple anisocoria is unknown. It may be intermittent or constant, and sometimes it goes away on its own.

404 image

Top: Normal pupils. Middle: Anisocoria with one pupil bigger than normal. Bottom: Anisocoria with one pupil smaller than normal.

SEE RELATED: Small pupils: What do they mean?

Pathologic anisocoria

Pathologic anisocoria is different pupil sizes due to an underlying condition or disease. Examples of conditions that cause anisocoria include:

Iritis

Iritis is a form of uveitis (an inflammatory disease of the eye). Acute iritis is characterized by:

  • Eye redness

  • Eye pain

  • Photophobia

  • Inflammation of the iris

  • A smaller pupil in the affected eye (anisocoria)

Iritis has many causes, including eye infection, underlying inflammatory diseases and trauma. Your eye doctor can treat the symptoms of iritis while the underlying cause of the condition is determined and controlled. 

In some cases, anisocoria from iritis can remain after the iritis has been successfully treated.

Horner's syndrome

Most people with Horner’s syndrome have these three signs: 

  • Ptosis (drooping eyelid)

  • Miosis (constriction of one pupil), causing anisocoria

  • Facial anhidrosis (loss of sweating around the affected eye)

Horner's syndrome also affects how quickly the smaller pupil dilates in dim lighting. Normal pupils (including normal pupils that are slightly unequal in size) dilate within five seconds of room lights being dimmed. A pupil affected by Horner's syndrome generally takes 10 to 20 seconds to dilate in dim lighting or a darkened room.

Horner's syndrome typically is caused by an underlying medical problem, such as a stroke, tumor or spinal cord injury. But in some cases, no cause can be found.

Adie’s tonic pupil

Adie’s tonic pupil is a dilated pupil caused by damage to nerve fibers that control muscles in the eye that constrict the pupil. The affected pupil also reacts poorly to light. Adie’s tonic pupil occurs primarily in women between the ages of 20 to 40 years. In 80% of cases, only one eye is affected, resulting in anisocoria. In most cases, the cause of Adie's tonic pupil is unknown.

Third nerve palsy

The third cranial nerve — also called the oculomotor nerve — controls several muscles that move the eyes and eyelids. It also influences a muscle that controls pupil size. Paralysis (palsy) of the oculomotor nerve causes the affected eye to have a dilated pupil, resulting in anisocoria. 

In addition to anisocoria, third nerve palsy also can cause:

  • Ptosis (drooping eyelid)

  • A “down and out” misalignment of the affected eye (strabismus)

  • Loss of accommodation (ability to focus on near objects)

Causes of third nerve palsy include:

  • Pressure on the oculomotor nerve from an aneurysm, tumor or brain hemorrhage

  • Migraine

  • Severe infections, such as meningitis 

If you or a family member develop symptoms of third nerve palsy, seek medical attention immediately.

SEE RELATED: Mydriasis: Definition and causes

Mechanical anisocoria

Mechanical anisocoria is unequal pupil sizes from damage to the iris or its supporting structures. Causes of this type of anisocoria include:

Congenital anomalies of the iris also can be a cause of mechanical anisocoria. Examples include:

  • Aniridia (a complete or partial absence of the iris of one eye)

  • Coloboma (a gap in the iris present at birth, giving the pupil a distinct “keyhole” or “cat-eye” appearance)

  • Ectopic pupil (an inherited condition that causes displacement of the pupil and dislocation of the lens)

Tumors inside the eye also can cause mechanical anisocoria. 

Pharmacologic anisocoria

Pharmacologic anisocoria is unequal pupil size that occurs as a side effect of a medication.

Drugs that have been identified as potential causes of pharmacologic anisocoria include:

  • Selective serotonin re-uptake inhibitors (SSRIs) used to treat depression

  • Transdermal scopolamine patches used to treat motion sickness and nausea from chemotherapy 

Certain glaucoma eye drop medications also can cause anisocoria, especially if they are used to treat glaucoma in just one eye. Examples of glaucoma medications that can cause anisocoria include:

  • Apraclonidine (larger pupil in the treated eye)

  • Brimonidine (larger pupil in the treated eye)

  • Pilocarpine (smaller pupil in the treated eye)

What to do if you have anisocoria

If you or someone else notices that you have unequal pupil sizes, see your eye doctor immediately — especially if you have any of the following:

  • Drooping eyelid (ptosis)

  • Double vision

  • Loss of vision

  • Headache or neck pain

  • Eye pain

  • Recent head or eye injury

If the anisocoria is minor and your pupils react normally to tests your eye doctor performs, there may be nothing to worry about. But you should have your unequal pupils evaluated by an eye care professional or neurologist before you assume all is well.

If you have anisocoria and one pupil is bigger than the other, ask your eye doctor about photochromic lenses. These eyeglass lenses will darken automatically in sunlight to reduce any light sensitivity (photophobia) you may be experiencing.

Photochromic lenses also will protect your eyes from harmful UV rays and high-energy blue light — especially the eye with the larger pupil if it doesn't react normally to light.

READ NEXT: What is a blown pupil?

Page published in March 2019

Page updated in November 2021

Dialated Eye Exam: Purpose, Procedure, Risks, Recovery

Your doctor wants to dilate your eyes. Do you really need it? Here’s what they’re looking for and how it may affect you.

By Stephanie Langmaid

Medically Reviewed by Whitney Seltman, OD on March 16, 2021

Dilation is part of a thorough eye exam. You may think it’s a hassle. But it gives your doctor a good look inside your eye. It’s especially important if you’re having eye pain or vision problems, or if you’re more likely to get certain eye diseases.

Normally, your pupil gets smaller when light shines into it. In dilation, your doctor uses special eye drops to force the pupil to stay open. This allows them to see much more of the back of your eye, including the entire retina, the part of the retina called the macula, and the optic nerve.

During a dilated exam, your doctor can spot problems like a torn or detached retina or an eye tumor. They can also diagnose and monitor common eye diseases that can take away your sight:

  • Diabetic retinopathy: Signs include blood vessels that leak, swell, or grow abnormally in the retina.
  • Glaucoma: Your doctor looks for damage to the optic nerve.
  • Age-related macular degeneration: Protein or pigment buildup and unusual growth of blood vessels are symptoms of a breakdown of the macula.
  • Cataract: A clouding of your natural lens.

Almost all of these conditions are painless, so you may not even know you have one unless you see your doctor and have your eyes dilated.  

Everyone’s eyes react differently to the dilation drops. It usually takes 15 to 30 minutes for your pupils to open completely. Most people are back to normal within about 4 to 6 hours. But for you, the effects could wear off more quickly, or they could last much longer.

Dilation doesn’t typically affect your distance vision, unless you are farsighted and don’t have glasses to correct your vision. But because your pupils can’t control the amount of light going into your eyes, the glare outside may bother you. For some people, that makes it unsafe to drive.

If you’ve never had your eyes dilated, get someone else to drive you home from your appointment. Once you’ve had it done, you’ll know whether dilation means you can’t drive after an exam.

Whether or not you get behind the wheel, it’s a good idea to bring sunglasses with you so you can shield your eyes after the exam.

Dilating drops make it hard for your eyes to focus on things close to you. You probably won’t be able to read, use the computer, or do other tasks that require near vision after your appointment, unless you wear bifocals or use reading glasses. If you work outside, the bright light may bother you. It may be easier to make an appointment later in the day so you don’t have to go back to work.

The National Eye Institute recommends everyone over 60 have a dilated exam once a year. If you’re African-American, you’re at higher risk for glaucoma, so the yearly recommendation starts at age 40. If you have diabetes, you should also have a dilated exam once a year no matter how old you are.

Dilation is often a normal part of an eye exam for people who wear glasses or contacts. But if you’re young and your eyes are healthy, you may not need it every time. Your doctor also may be able to use other methods to check your retina without dilating your eyes, but they may not work as well. See what your doctor recommends.

Many eye diseases are more common as you get older. The American Academy of Ophthalmology says everyone should get a baseline exam with dilation when they’re 40. That way, your doctor can track any changes that could signal a problem.

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My Pupils Are Dilated: What Do I Do Now? Is This Normal?

05-05-2021 · There are many reasons to have large pupils. I’ll list as many as I can think of. Being young: our pupils tend to be larger when we’re young. Fun fact: women used to put the juice of the belladonna (beautiful woman in Italian) plant in their eyes to make their pupils big and therefore more seductive.

05-05-2021

Many people have questions about their pupils before, during and after an eye exam, especially after they have been dilated. In this blog post, I will talk about the truly amazing function of your pupils – the little black holes that let light in your eye.

We will discuss:

  • Why pupils dilate
  • How pupils dilate
  • Why sometimes pupils are large
  • What medications affect our pupil size
  • What we should do if our pupils are large
  • When should I worry or seek out an eye doctor about my large pupils
  • Did I take something that made my pupils small or large
  • Why sometimes one pupil is larger than the other

Pupils are an amazing structure in our eyes that have been created through millions of generations of animals over hundreds of millions of years. They allow us today to see things that even the most expensive cameras in the world have trouble seeing. We can see in extremely low light, extremely bright light, and everything in between. They are affected by your mood, medications, drugs, and of course the ambient light. They change throughout our lives and are very much a part of our personality.

Healthy, normal pupils should constrict briskly and equally to light and dilate when the light is withdrawn. Both pupils should constrict when light is shined in one. This is called the pupillary light reflex, and is an involuntary reaction originating from your brainstem, which is why it’s called a reflex. It doesn’t need you to be conscious, and is a very helpful physical exam sign that should be understood by all doctors, not just eye doctors. If your pupils don’t react normally, your doctor should know the possibilities that the abnormal reaction implies, and know what to do to help.

Some people incorrectly spell dilated “dialated” which is understandable, because it is round like a dial, but it is spelled “dilated.”

There are many reasons to have large pupils. I’ll list as many as I can think of.

  • Being young: our pupils tend to be larger when we’re young. Fun fact: women used to put the juice of the belladonna (beautiful woman in Italian) plant in their eyes to make their pupils big and therefore more seductive. Probably also to make men more attractive to them since they’d be blurry. That’s a dad-joke! But the medicine is no joke. The plant is highly toxic.
  • Medications/drugs: there is a very long list of medications that can make our pupils bigger, starting with the ones we use to perform a dilated eye exam.
  • To dilate our patients’ pupils, we use:
    • Mydfrin- generic name: phenylephrine
    • Mydriacyl- generic name: tropicamide
    • Scopolamine
    • Atropine (usually used therapeutically, not diagnostically-see below)
  • Many other medications that affect your nervous system can also make your pupils larger or smaller, although generally the effect is a lot less than what we eye doctors use:
    • Antihistamines
    • Decongestants
    • Parkinson’s medications
    • Motion sickness medications
    • Tricyclic antidepressants
    • Anti-seizure medications
    • Flomax (Tamsulosin) for prostatic hypertrophy can cause “Floppy Iris Syndrome” that can make cataract surgery more difficult.
  • Drugs:
    • Cocaine was formerly used to dilate pupils, and is still potentially useful, although difficult to obtain, even for doctors, in the diagnosis of a condition called Horner’s syndrome.
    • LSD
    • Amphetamines
    • Ecstasy
  • Mood: although the effect of your mood on your pupils is short-lived, it can either dilate or constrict your pupil.
  • Previous eye conditions, eye trauma, or eye surgery that has left your pupils irregular or different looking: Inflammatory conditions such as iritis (inflammation of the iris) that can occur from many different reasons, can leave you with adhesions to the lens of your eye called synechia.  These can sometimes be broken with dilation or a surgical procedure to break the stickiness.
  • Congenital (born with it) irregular pupils: such as an iris coloboma, which occurs when your eyes don’t fully develop the iris sphincter in utero (when your mom is pregnant with you). It most frequently occurs in the lower portion of the iris, and has been called a “keyhole” iris.
  • A prosthetic eye: if someone has lost an eye, hopefully the prosthetic eye is so real looking that it may not be readily detectable.  If so, the pupillary will of course not dilate, which may make the size of the pupil in the healthy eye a different size. When in a bright or dim environment.

Why do I need to have my pupils dilated?

As a part of a complete eye exam, we put medication in your eyes to relax the pupillary sphincter and/or stimulate the radial muscles of your iris (the colored part of your eyes) to make them large so we can see inside your eye. This allows us to diagnose problems of the retina (the light-sensitive layer that lines the back of our eye and acts like film in a camera (for those of us who remember when cameras had film in them!)

How does pupil dilation help my eye doctor?

The other major reason we dilate your pupils is to refract you. Sounds scary, but it just means we measure your eyes for the amount of farsightedness, nearsightedness, and astigmatism. Your focusing muscles are relaxed with the drops so they don’t affect the measurements. This wears off in a few hours.

Why can’t I see when I have dilated eyes?

The medications we as eye doctors administer to dilate your pupils also relax the focusing muscles that change the shape of the lens of our eyes and add focusing power that we need to see near objects. If you’re nearsighted, you may be able to see better when you remove your glasses. Don’t worry, the effect wears off in a few hours.

Why do pupils dilate?

Anatomically our pupils have two opposing sets of muscles, just like other parts of our bodies. Our triceps oppose our biceps, hamstrings oppose our quadriceps and so on, so we can flex and extend our body parts. Our pupils have a sphincter, a round muscle that pulls the iris centrally like a purse string and makes it smaller. We also have radial muscles of the iris, which are like spokes of a wheel. When they shorten/constrict, they pull the iris away from the center and make our pupils bigger. When we dilate pupils, we give you eye drops that stimulate the radial muscles and relax the sphincter muscles. Et voilà, your pupils enlarge within a few minutes.

Dilated Pupils scared my regular doctor!

In medical shows, and IRL (in real life) you may see the doctor shining a light into an accident victim’s eyes. There are several things that can be determined by this physical exam component. One of the scary ones is pressure on the part of the optic nerve that constricts the pupil. If this constriction is impaired, it may indicate a life-threatening condition such as a ruptured aneurysm, hemorrhagic stroke, or increased intracerebral pressure from a head injury or other trauma. If immediate action is not taken, the patient could quickly die.

I just naturally have big pupils. Why are my pupils so big?

Yes, this occurs in people, generally younger ones, and is part of normal variation in people. Isn’t it wonderful!?

My dilated pupils took days to wear off!

Sometimes this just happens. Generally, the lighter your irises, the longer it takes to metabolize the medications, and it could be that it took that long. Also, there is a medication called Atropine that may have been used. In my practice, I rarely use Atropine eye drops, and I never use it for routine dilation. I use it only when my patient has an inflammatory or traumatic eye condition and we need to relax the eye muscles so their eye can heal. Sort of like putting your arm in a sling if you sprain or break your wrist. Atropine can take up to a week to wear off. There are a couple other similar longer-lasting medications such as Hyoscine and Scopolamine (also used for seasickness).

One of my pupils dilated more than the other one. What’s up with that?

The medical term for different sized pupils is “anisocoria.” There are many reasons for this, but if you don’t know why this is happening, you should definitely let your eye doctor know right away. Sometimes it’s physiologic anisocoria, which just means that’s your normal, but there are many reasons why this may not be normal, and you should have a highly competent eye doctor do a very careful exam. If it’s not normal, figure that out and get the help you need.

I hope this has helped you understand a little more about your pupils, the miraculous little opening in the center of your eyeball that regulates the amount of light entering your eye, helps focus light, and helps you see near objects better.

Signature of Dr. Matthew Sharpe, MD

– Dr. Matthew R. Sharpe

backyardchickens.com

Dilated pupils are large, but constricted pupils are small. As light hits the eye, the pupil should become smaller or consrticted, then grow larger or dilate in darker areas. Can you post a picture? With Mareks disease there can be pupil size and shape changes, as well as iris color changes.

Sep 28, 2015
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Hi everyone
I have seven beautiful and much loved Isa Browns in Adelaide, Australia. They are healthy free rangers. But I noticed yesterday that one of them has very small, dilated pupils in her eyes. This must have changed sometime over the last month. She doesn't appear to be vision impaired in any way, is eating, drinking and laying normally. Does anyone have any knowledge they could share? Thank you so much. Ali
Apr 3, 2011
62,634
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Welcome to BYC. Dilated pupils are large, but constricted pupils are small. As light hits the eye, the pupil should become smaller or consrticted, then grow larger or dilate in darker areas. Can you post a picture? With Mareks disease there can be pupil size and shape changes, as well as iris color changes.
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Normal eye on left, ocular Mareks disease on right
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Normal eye in middle; ocular Mareks on left and right
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Ocular Mareks
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Sep 28, 2015
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South Australia
Thank you for your reply. You're right, it's actually a constricted pupil - not dilated! My girl looks exactly like the chicken in the photo. I'm really worried it's Marek's. I'll take her to the vet today to be sure. Is there anything I can do if this is confirmed to be the case? I am also really worried about my six other girls, as my googling on this leads me to believe it is quite contagious in a flock.
Thank you so much for any info or experience you may have.
Apr 3, 2011
62,634
55,747
1,322
southern Ohio
Can you try to get pictures of her eyes from the side? Some BYCers have seen ocular Mareks, and may be able to help. I wouldn't panic about it being Mareks just yet. Ocular Mareks is just one of 4 types of Mareks. There can be many other eye disorders. I will give you some links a little later to read.
Sep 28, 2015
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Thank you so much. Here are some photos of my beautiful girl and her unusual eye. I hope they're clear enough for you to see.
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Sep 28, 2015
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Thank you for all your help. After a visit to the avian vet, I'm thrilled and ever so relieved to let you know that it's not Marek's. Phew! We are on some anti-biotics, eyedrops and pain killers for an eye inflammation. Hopefully we will see some positive results within the next week or so. It's amazing how attached we become to these beautiful creatures, isn't it?! They are so precious. I'm so glad I have them. Thanks again for your feedback and support. Much appreciated.

Ali

pets-animals.blurtit.com

Answer (1 of 8): A cat's eyes being dilated can be a sign of illness elsewhere in their bodies. If you have a cat with one dilated and one is not, there are a number of things that could be wrong. There are a number of over the counter medications that you can try but if they do not do the trick you may need to take your cat to the veterinarian, it may be an indicator of other problems.Cats ...

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8 Answers

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A cat's eyes being dilated can be a sign of illness elsewhere in their bodies. If you have a cat with one dilated and one is not, there are a number of things that could be wrong. There are a number of over the counter medications that you can try but if they do not do the trick you may need to take your cat to the veterinarian, it may be an indicator of other problems.Cats can develop a number of eye problems such as cat herpes and cat glaucoma as well as cat leukemia and feline immunodeficiency disease. If your cat is developing problems such as these there are a number of over the counter cat eye drops that can relieve most common eye problems cat s experience. The problem can either be viral or bacterial based, so check the instructions on any medication you buy to make sure you know what you are buying. There are many different diseases that can affect your cats eyes and therefore its health. Since cats are just like us and only have one set of eyes to work with, it is imperative that you monitor this part of your cat's health very carefully. If over the counter medication does not clear the problem up within a couple of weeks, you need to seriously consider taking your cat to your local veterinarian. Since a problem with a cat's eyes can indicate a general health problem, it could very well be an alert that there is something seriously wrong with your pet.

If you take care of your pet cat like you would a family member, and they are indeed a part of your family, they will be around to give you years of love and enjoyment and they'll be happier too when they feel healthy and happy.

thanked the writer.

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This is called anisocoria--when the pupils are different sizes.  It can be caused by neurological problems, trauma, Horner's syndrome, and primary ocular diseases.  Your cat needs to be examined by a veterinarian to determine the cause and start treatment if appropriate.  Not all causes of anisocoria are benign.

thanked the writer.

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This is either a blind eye, or your cat has a head injury. This should not be ignored, take the cat to a vet.

thanked the writer.

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It could be blind in one eye. There is no reason to get rid of it, I have a cat who is totally blind, but she can see shadows. Her eyes also do not dilate at all, and they look kinda creepy that's why she weird most people out. She looks like she's staring through you, Lol. ^_^

thanked the writer.

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My cat has that too

thanked the writer.

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Your cat had a stroke, also known as cerebral vascular accident

thanked the writer.

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My cat developed a dilated pupil also. Her mouth droops on the same side of the dilated pupil. She also has a tumor or cancer in her lower mandible on the same side. I think the tumor or cancer came first. It is getting larger. Has difficult time eating but still meows and walks around and purrs and talks to me. Poor baby. My sister and dad said dilated pupil is a stroke. She is old.

thanked the writer.

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My cat has one eye that is less dilated the the other. It seems to be all the time. He is an indoor cat and has never been outside

thanked the writer.

Why Do I Need My Eyes Dilated? - Northwest Eye Center, PC

24-01-2020 · Why Do I Need My Eyes Dilated? Dilation is part of a thorough eye exam. You may think it’s a hassle. But it gives your doctor a good look inside your eye. It’s especially important if you’re having eye pain or vision problems, or if you’re more likely to get certain eye diseases.

24-01-2020

Dilation is part of a thorough eye exam. You may think it’s a hassle. But it gives your doctor a good look inside your eye. It’s especially important if you’re having eye pain or vision problems, or if you’re more likely to get certain eye diseases.

Normally, your pupil gets smaller when light shines into it. In dilation, your doctor uses special eye drops to force the pupil to stay open. That allows him or her to see much more of the back of your eye, including the entire retina, the part of the retina called the macula, and the optic nerve.

During a dilated exam, your doctor can spot problems like a torn or detached retina or an eye tumor. They can also diagnose and monitor common eye diseases that can take away your sight:

  • Diabetic retinopathy: Signs include blood vessels that leak, swell, or grow abnormally in the retina.
  • Glaucoma: Your doctor looks for damage to the optic nerve.
  • Age-related macular degeneration: Protein or pigment buildup and unusual growth of blood vessels are symptoms of a breakdown of the macula.
  • Cataract: A clouding of your natural lens.
  • Hypertension: High blood pressure can cause damage to the blood vessels in the retina.
  • Eye tumors: Ocular tumors are tumors inside the eye. They are collections of cells that grow and multiply abnormally and form masses.

How Long Does It Last?

Everyone’s eyes react differently to the dilation drops. It usually takes 15 to 30 minutes for your pupils to open completely. Most people are back to normal within about 4 to 6 hours. But for you, the effects could wear off more quickly, or they could last much longer.

Can I Drive?

Dilation doesn’t typically affect your distance vision. But because your pupils can’t control the amount of light going into your eyes, the glare outside may bother you. For some people, that makes it unsafe to drive.

If you’ve never had your eyes dilated, get someone else to drive you home from your appointment. Once you’ve had it done, you’ll know whether dilation means you can’t drive after an exam.

Whether or not you get behind the wheel, it’s a good idea to bring sunglasses with you so you can shield your eyes after the exam.

Can I Go Back To Work?

Dilating drops make it hard for your eyes to focus on things close to you. You probably won’t be able to read, use the computer, or do other tasks that require near vision after your appointment, unless you wear bifocals or use reading glasses. If you work outside, the bright light may bother you. It may be easier to make an appointment later in the day so you don’t have to go back to work.

Can Advanced Technology Replace Dilation?

Many eye practices will say “No Dilation Necessary. New State of the Art Technology Available.” Doubtless, “no dilation” appeals to patients who don’t like getting dilated, with the time and discomfort required. But there are dangers to this approach.

Advanced technology, like Optomap, offers greater power to diagnose and manage ocular disease, but think twice before you use it as a replacement for dilation. There is no technology that replaces dilation for thoroughly assessing eye health.

There are limitations to the device. One of the main limitations is that it does not image all of the retina. There are parts of the retina superiorly and inferiorly that are missed by Optomap, usually because those areas seem to be limited or blocked by the upper and lower lids.

In 2017 a study was published in Seminars in Ophthalmology, which examined 36 eyes of 34 patients, and retrospectively compared the use of Optomap to indirect ophthalmoscopy (dilated eye exam) in evaluating patients with a history of with non-traumatic retinal detachments. The study found that “ultra-widefield imaging failed to detect retinal pathology in the superior and inferior quadrants in 11.1% and 19.4% of cases, respectively [and in] postoperative imaging, UWF photos did not detect retinopexy scarring which was ophthalmoscopy-visible both superiorly and inferiorly in 19.4% of cases.”

The study concluded that while “ultra-widefield imaging is a useful adjunct for documentation of retinal detachments and their postoperative repair, the detection of retinal holes, tears, and postoperative scarring is poor, especially in the inferior and superior periphery.”

How Often Do I Need It?

The National Eye Institute recommends everyone over 60 have a dilated exam once a year. If you’re African-American, you’re at higher risk for glaucoma, so the yearly recommendation starts at age 40. If you have diabetes, you should also have a dilated exam once a year no matter how old you are.

Dilation is often a normal part of an eye exam for people who wear glasses or contacts. But if you’re young and your eyes are healthy, you may not need it every time. Your doctor also may be able to use other methods to check your retina without dilating your eyes, but they may not work as well. See what your doctor recommends.

Many eye diseases are more common as you get older. The American Academy of Ophthalmology says everyone should get a baseline exam with dilation when they’re 40. That way, your doctor can track any changes that could signal a problem.

Schedule Your Next Eye Exam
Why Are My Cat's Eyes Dilated All the Time? (Cat Pupil ...

23-12-2021 · Cats dilate their pupils to improve their vision. Wide eyes enable cats to absorb more light, which is beneficial in dim lighting. Pupils also dilate when cats are excited, afraid, […]

23-12-2021

Cats dilate their pupils to improve their vision. Wide eyes enable cats to absorb more light, which is beneficial in dim lighting. Pupils also dilate when cats are excited, afraid, or hurt. This should never last longer than a couple of hours.

Constant dilation of cats’ eyes can signify pain, overstimulation, or age-related atrophy. Various health concerns are connected to dilated pupils, including feline leukemia, toxicity, dysautonomia, and tumors.

Cats’ eyes should dilate periodically, so it’s a real concern if the pupils never contract. If this happens, your cat’s eyesight could be at risk. Diagnosing and treating the issue is key to maintaining good feline eye health.

Why Do Cat’s Eyes Dilate?

Most commonly, cats widen their eyes to see more clearly in dim conditions.

Light enters cats’ eyes through the pupils—the more light, the better they can see. So, a cat may seem to have constantly dilated pupils at night.

According to Brain Research, cats’ pupils expand up to 10 times wider than those of humans. Dilated pupils are known as mydriasis. If lighting is not dim, a cat will widen its pupils for a different reason.

These include the following:

  • Shocked or startled
  • Excited
  • Pain
  • Unwell
  • Eye trauma

If the dilation is temporary, it’s not a concern. Your cat could be in pain because somebody stepped on its tail. Likewise, your cat will quickly recover from being startled by a loud noise.

My Cat’s Eyes Are Constantly Dilated

Cats’ eyes should remain in a neutral state for the majority of the day. Dilation of the eyes should be an exception, not the general rule. Cats’ eyes could remain dilated throughout the day and night for medical or psychological reasons.

Common explanations include:

  • Blindness
  • Generalized anxiety disorder
  • Overstimulation
  • Chronic or constant pain
  • Consumption of toxins
  • Hypertension (high blood pressure)
  • Dysautonomia (Key-Gaskell Syndrome or Feline Dilated Pupil Syndrome)
  • Side effects of medication
  • Age-related atrophy of the iris
  • Ocular tumors
cats eyes suddenly dilated

Loss of Sight

If a cat’s losing its sight, its eyes will remain dilated constantly. The cat is attempting to absorb as much light as possible to aid its vision.

Senior cats start to lose their sight, especially purebred cats. The blindness could be temporary or permanent.

Aside from constantly dilated pupils, signs that a cat is going blind include:

  • Clumsiness and bumping into unfamiliar objects.
  • Walking with whiskers low to the ground.
  • Apprehension when jumping and climbing.
  • Easily startled by sudden noises.
  • Difficulty locating a water source.
  • Excessive vocalization, growing distressed when you do not respond.

You can test your cat’s eyesight with this simple test:

Wave a ball of wool before the cat’s eyes. Don’t swing the wool close enough for the cat’s whiskers to sense it. If your cat can see, its hunting instincts will be initiated. A blind cat will, of course, remain indifferent.

If your cat has lost its sight, the problem may be temporary. Kidney issues, toxicity, feline herpesvirus, and eye infections can cause short-term blindness.

If your cat is permanently losing its sight, it’ll learn to cope. Eyesight is widely considered to be a cat’s least effective sense. Cats rely more on hearing, smell, and touch.

The following will help:

  • Do not rearrange the furniture.
  • Provide obstacle-free paths to food, water, and litter.
  • Stamp your feet when entering a room to announce your presence.
  • Speak to your cat regularly as your voice will offer comfort.
  • Avoid loud, sudden noises.

Tension and Anxiety

When a cat is frightened, its eyes will remain wide and dilated. A cat with anxiety will have constantly dilated pupils.

If you notice wide-eyed fear in your cat, you’ll need to identify the trigger. This could range from a loud noise to the presence of a stranger. Cats will also frequently flee and hide when startled. When the cat re-emerges from its hiding place, its eyes should no longer be dilated.

A cat that roams with dilated eyes seems continuously on edge. The cat fears danger at every turn. Health problems can follow prolonged periods of stress and anxiety. The cat may also become more aggressive.

Discover why the cat is stressed and make adjustments. Most often, cats are stressed because something in their routine has changed. Maintain a strict, reliable routine to keep your cat happy and contented.

Some cats are nervous by nature, so utilize medication, calming scents and sounds, and herbal remedies to calm your cat.

Overstimulation

If a cat is not nervous, it could just be overstimulated. Cats grow excited due to sights, sounds, and smells. If it does not calm down, it will grow over-excited, placing a strain on the heart.

Overstimulation is common when a cat finds itself in a new environment. The cat will grow excitable while exploring new surroundings. If you notice a new cat has constantly dilated eyes, guide it to a single room.

Once the cat has had a chance to calm down, its pupils will normalize.

Chronic Pain

Cats are adept at hiding physical pain. For example, a cat that cannot walk without limping may not walk at all.

Cats cannot hide all the symptoms of pain, and constantly dilated cats’ eyes are a giveaway. If your cat’s eyes are wide, look out for other symptoms of discomfort.

These include the following:

Make your cat comfortable and attempt to decipher the problem. In senior cats, arthritis is an ever-present risk, but this can be managed through massage, soft blankets, and nutritional supplements. Prescription painkillers will also be available.

If the cat has foul breath, it may be experiencing dental pain. Most cats will eventually experience problems with their teeth, and dental issues can be connected to health complications.

Toxicity and Poisoning

A cat that has consumed toxins will have dilated eyes.

Aside from eye dilation, warning symptoms of toxicity include:

  • Vomiting and diarrhea
  • Trouble breathing
  • Weakness and lethargy
  • Muscle tremors
  • Low body temperature
  • Lethargy
  • Reduced appetite

Toxicity is an ever-present risk because many home/yard items are toxic. If your cat has consumed toxins, these must be flushed from the body.

Hypertension

If a cat’s blood pressure is 160/80 mmHg, it has hypertension. Older cats are prone to high blood pressure, and the pain and discomfort associated with the condition can lead to dilated eyes.

Hypertension is often a secondary disease. It can be linked to another health concern, such as kidney or heart problems.

Aside from dilated eyes, other symptoms include:

  • Excessive water consumption
  • Blood in the urine
  • Circling
  • Bleeding from the nose
  • Irregular heartbeat
  • Muscle tremors
  • Seizures

A cat that takes medication for hypertension will experience a reduction in symptoms. Unfortunately, the cat may still have dilated eyes. According to the Archives of Pharmacology, mydriasis is a side effect of Clonidine, a drug used to treat hypertension in cats.

Dysautonomia

Dysautonomia, also known as Key-Gaskell Syndrome or Feline Dilated Pupil Syndrome, attacks a cat’s automatic nervous system (ANS). This means that a cat has no control over its basic functions.

As an aggressive and degenerative condition, dysautonomia must be treated urgently. Constantly dilated eyes are the easiest symptom to recognize.

Other concerns include:

  • Digestive issues
  • Dry nose
  • Lack of appetite and associated weight loss
  • Regurgitation of food
  • Protrusion of the eyelid
  • Slow heart rate
  • Low body temperature
  • Inability to urinate or defecate

The Journal of Feline Medicine and Surgery describes an enlarged esophagus and swollen abdomen as the most common warning signs. Be mindful of a wide-eyed cat that vomits regularly or regurgitates its food.

Iris Atrophy

As a cat grows older, its iris’ starts to thin. Once the iris degenerates, your cat will become unable to contract its pupils anymore.

Iris atrophy is irreversible, but the cat will not be in pain. It may become sensitive to bright light, though. The cat will squint and hide in dark corners, so provide an escape route from illuminated areas.

Ocular Cancers and Tumors

When a cat develops a tumor behind the eye, it will often be malignant. This tumor can spread throughout a cat’s body. This will be painful for your cat, leading to dilated pupils.

Other symptoms include:

  • Discoloration
  • Inflammation
  • Glaucoma
  • Discharge from the eye
  • Misshapen iris
  • Cloudy eyes

The diagnosis of eye tumors is completed using an ophthalmoscope. Biopsies will then be taken to determine the severity of the tumor.

If the tumor is small, it may be treatable by laser. However, eye removal will be necessary to prevent the tumor from spreading in most cases.

Only One of My Cat’s Eyes is Dilated

Mismatched pupil sizes in cats mean your cat has anisocoria. Sometimes, one pupil is smaller and permanently narrowed. It’s more common for one eye to be permanently dilated, so your cat may keep one eye closed.

Senior cats are prone to developing anisocoria. Anisocoria is a symptom of another problem.

Common explanations include:

  • Physical trauma
  • Glaucoma
  • Ulcers on the cornea
  • Disease and infection within the eye
  • Feline spastic pupil syndrome

As with dual-dilated eyes, anisocoria is concerning if it becomes a prolonged condition. Trauma, such as being poked in the eye, can cause temporary anisocoria. This should not last longer than a few hours, though.

If the anisocoria lasts over 24 hours, your cat should be checked by a vet.

What do dilated cats eyes mean?

Eye Diseases, Ulcers, And Infections

Cats can be prone to a range of eye infections and diseases. They could be bacterial or due to irritation or allergies.

A basic eye infection can be treated with antibacterial eye drops. If successful, your cat’s eyes will return to an equal size.

Senior cats often develop ulcers on the eye, which can be removed by a vet using a scalpel. Ulcers are painful but can be treated.

A problem like glaucoma is more concerning. Glaucoma places pressure on your cat’s optic nerves. Left untreated, this could cost your cat its sight.

Feline Spastic Pupil Syndrome

This condition causes anisocoria to move from one eye to another. Feline spastic pupil syndrome is usually a symptom of feline leukemia (FeLV). If a cat’s mismatched eyes vary regularly, it likely has FeLV.

Feline leukemia is a contagious condition that’s passed on through blood, saliva, or waste. If recurrent, the condition is life-threatening. FeLV is a vaccine offered to all kittens and adult cats. Additional symptoms include:

  • High fever
  • Trouble breathing
  • Loss of appetite and weight loss
  • Pale and discolored gums
  • Sterility
  • Lethargy
  • Poor quality coat

There is no cure for FeLV, which is why vaccination is vital. If your cat is diagnosed with FeLV, you should keep it indoors. If the cat is infected once, it could catch the virus again. Mixing with other cats increases the risk.

Cats have very expressive eyes. You will often see a cat with dilated eyes when excited, but a cat’s eyes should never be dilated constantly.

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Why Do I Need to Get My Eyes Dilated?: Retina Specialists ...

Retina Specialists Blog Why Do I Need to Get My Eyes Dilated? If you come to see one of our ophthalmologists for an eye exam, the doctor may dilate your eyes as part of that exam. The good news is that it allows us to examine your eye structures to look for potential diseases and other problems. The bad news is that your vision may be fuzzy for ...

Why Do I Need to Get My Eyes Dilated?

If you come to see one of our ophthalmologists for an eye exam, the doctor may dilate your eyes as part of that exam. The good news is that it allows us to examine your eye structures to look for potential diseases and other problems. The bad news is that your vision may be fuzzy for a few hours afterward. Is dilation really necessary?

At Retina Specialists, with five locations around Dallas, Texas, our team of expert ophthalmologists wants to ensure that your vision is clear and your eyes remain healthy. That’s why they stress the importance of getting your eyes dilated when you come in for a comprehensive exam or with an injury or other potential problem. 

We’d like to explain why dilation is so important.

How the eye looks

To understand how your vision is supposed to work, it helps to know something about the eye’s structure and each part’s function. The best way to learn is to follow light’s path. 

Incoming light hits the eye’s surface, which is covered with a clear, curved, and tough membrane. While the clear area lets the light pass through, the curved area (cornea) protects the eye while focusing the light.

The focused light moves through the anterior chamber, a space filled with a fluid called the aqueous humor. Next, it travels through the pupil, and then through a lens that fine-tunes the focusing. Finally, it travels through the vitreous, another fluid-filled chamber, striking the back of the eye in a region known as the retina.

The retina converts the received images into electrical signals, which it sends to the brain through the optic nerve. Your brain decodes the image, allowing you to “see.”

The macula is the central 2% of the retina that registers your clear, central vision.

What is a comprehensive eye exam?

A standard eye screening simply evaluates your vision, and the doctor may prescribe glasses or contact lenses as a result. 

A comprehensive eye exam, on the other hand, is a complete eye exam; it evaluates vision as well as the health of your inner and outer eye. Dilation is a critical part of the exam, as it allows the ophthalmologist to look at the inner eye structures and determine if there’s any malformation or disease.

Why is dilation included?

Your pupil’s normal reaction when exposed to light is to get smaller, so if our doctor just shines a brighter light into your eye, we won’t be able to see a thing. To dilate the eye, we use special eye drops that force the pupil to stay open despite the light. Now, we can see all the way to the back of your eye, including the entire retina, macula, and the optic nerve.

During a dilated exam, we can detect problems like a torn or detached retina (which, if not treated, could create a loss of vision), the development of an eye tumor, trauma, or malformed structures. 

We can also diagnose and monitor common eye diseases:

  • Diabetic retinopathy: blood vessels that leak, swell, or grow abnormally in the retina

  • Detached retina: area of the retina pulls away from the connecting tissue

  • Detached vitreous humor: often causes eye floaters (spots in vision)

  • Glaucoma: damage to the optic nerve

  • Age-related macular degeneration (AMD): protein or pigment buildup and unusual growth of blood vessels destroy the macula and central vision

  • Cataract: clouding of your natural lens

Almost all of these conditions are painless, so you may be unaware you have a problem unless you get your eyes dilated.

What should I avoid if my eyes are dilated?

It usually takes 15-30 minutes for your pupils to open completely once the drops are in, and the effects last for about 4-6 hours, though everybody’s response is a bit different.

Dilating drops don't usually affect your distance vision, unless you're farsighted and don't wear glasses. What they do is make it hard for your eyes to focus on things close up. That means you probably won’t be able to read well, use your phone or computer, or do other near-vision tasks — unless you wear bifocals or reading glasses. So on the day of your exam, one way to avoid missing work is making your appointment for later in the day.

Dilating drops also increase your light sensitivity, since the pupils remain open. Definitely wear sunglasses to reduce the glare, and try not to look at any bright lights. You also shouldn’t drive, both because of the glare and because parts of your vision will remain fuzzy for a few hours.

If you haven’t had a dilated eye exam in a while, or it’s time for your next one, Retina Specialists is the place to go. Give us a call at any of our offices to set up an appointment for your exam, or book online with us today.

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Why Are My Cat's Eyes Always Dilated? (Vet's Explanation)

15-09-2021 · What Causes a Cat’s Eyes to Dilate? High stress levels. For example, a cat who is in extreme pain or who is very anxious about being in a vet clinic will... dim light. In dim light, it is normal for pupils to dilate in an attempt to allow the maximum amount of light in. Iris Atrophy. Iris atrophy ...

15-09-2021

Why are my cat’s eyes always dilated?

A cat is able to constrict and dilate its pupils, just like you and I.

This controls the amount of light entering their eyes and is important for vision in bright and dim lighting.

If a cat’s eyes are always dilated, there is likely something amiss, so read on to learn more about the causes.

READ MORE: Why Does My Cat Headbutt Me in the Morning?

What Causes a Cat’s Eyes to Dilate?

cat with dilated pupils

Scientifically speaking, when the pupils do not constrict back to regular size, this is called ‘mydriasis’. Dilation of the pupils of the eye should occur in certain circumstances but should never be a permanent change.

In a healthy cat, we will see temporary pupil dilation due to:

High stress levels

For example, a cat who is in extreme pain or who is very anxious about being in a vet clinic will have large, black eyes. Once your kitty calms down and is feeling back to normal, its pupils will constrict.

dim light

In dim light, it is normal for pupils to dilate in an attempt to allow the maximum amount of light in.

However, as soon as the level of light increases, the pupils constrict right down. You should see your vet check for this response by shining a small flashlight into the eyes.

Iris Atrophy

Iris atrophy that occurs in elderly cats can lead to larger pupils. The colored part of the eye is also called the iris. This naturally thins out in our senior kitties.

The weaker muscle is less capable of constricting pupils. While your senior cat is in no danger from its iris atrophy, it is important to confirm the diagnosis with a vet.

Medication

Medication side effects are another consideration. For example, if atropine drops have been applied, the pupil will dilate temporarily.

READ MORE: Why Do Cats Purr When You Pet Them?

7 Reasons Why Cats Eyes Always Dilated

black kitten with dilated eyes

Why are my cat’s eyes always dilated? This is a question many cat owners ask me with concern in their voices.

Certainly, noticing something unusual is always cause for anxiety and needs to be looked into.

A cat with dilated pupils could have a range of medical conditions and common explanations include:

#1 High Blood Pressure

High blood pressure in cats can be hard to diagnose as signs are not always obvious.

We most commonly see high blood pressure in geriatric cats, particularly those with an underlying condition such as hyperthyroidism or kidney failure.

A cat’s blood pressure should be between 120-150 mm HG, but those with hypertension often have regains over 180mm HG.

High blood pressure is usually treated with oral medication and it is important to address any underlying medical conditions.

#2 Blindness

A cat with dilated pupils may actually be blind. Warning signs can include sudden disorientation, inability to find their litter box and food bowl, banging into objects, and not wanting to move about.

Sudden vision loss is a true emergency and warrants an immediate vet visit.

Certain ocular issues, such as a detached retina, can be treated successfully if your cat is seen promptly and does not have to result in permanent blindness.

#3 Key-Gaskell Syndrome

Also known as feline dysautonomia, affects the autonomic nervous system and can be diagnosed in cats of any age. Signs are wide-ranging and can include e.g. diarrhea, dry eyes, and dehydration.

Sadly, this condition has a poor prognosis and only a small number of cats make a full recovery once severely affected.

#4 Chronic Pain

Any ongoing physical pain that is causing your pet distress can be the reason for a cat’s eyes being always dilated.

It isn’t always easy for an owner to localize pain but a veterinary expert should be able to find the source. The vet will check for more common causes of pain including joint disease and dental disease.

#5 Toxin ingestion

A variety of toxins will affect the nervous system causing dilated pupils including permethrin and certain anti-depressants.

Most cats will also experience additional signs of toxicity including vomiting, tremors, and irregular heart rhythms.

#6 Increased intra ocular pressure

Increased intra ocular pressure can cause intense pain. It is advised that this pressure is measured in ALL feline patients with dilated pupils. Causes for glaucoma include uveitis, tumors, and lens dislocation.

#7 Physical trauma

i.e. eye trauma can lead to pupil dilation which may be permanent or temporary. A fall from a height or road traffic accident can be to blame.

READ MORE: 12 Cat Sleeping Positions

If my cat’s eyes are always dilated, what test will the vet run?

Tuxedo cat with orange dilated eyes

Diagnostic tests will be needed to determine why your cat is unable to constrict its pupils and has large, dark eyes.

Initially, your cat will take a full clinical history and will look back on any medical records available.

Next, they will perform a thorough physical exam. After, they will focus on your cat’s eyes.

Tests will include checking the Pupillary Light Reflex (shining light to assess the pupil’s ability to change size; pupil size should change quickly), Dazzle Reflex (assessing if your cat reacts to bright light), and Menace Response (checking vision by performing a threatening hand gesture towards the eye, to see if your cat reacts).

They should use an ophthalmoscope to assess the optic nerve and retina.

Your vet may also perform a neurological exam, to assess your cat’s nervous system. It is likely the eyes will be stained with a Fluorescein dye to assess for any corneal scratches or ulcers.

Additional testing such as checking the intraocular pressure and swabbing any ocular discharge should also be performed.

Check: Why Do Cats Groom Each Other?

What is the prognosis for my cat with dilated pupils?

Tuxedo cat with large dilated pupils

As there is a wide range of causes for a cat whose pupils will not constrict, the prognosis varies greatly.

For example, a cat whose pupils keep dilating due to stress is exhibiting a normal reflex and is not unwell.

A cat who has dilated pupils due to medication will make a full recovery once the medicine has been stopped.

Conversely, if your cat has a serious neurological disease such as Key-Gaskell Syndrome, their prognosis is poor.

What if only one of my cat’s pupils is dilated?

The medical term for this is ‘anisocoria’. When one pupil is larger than the other (which remains normal size), there is an underlying issue.

Of course, it is possible that one eye is more constricted than the other, but this is a lot less common.

Oftentimes, the cause is localized to the affected eye. There could be a foreign body under the eyelid, a corneal ulcer, severe eye infection, uveitis, or a tumor that is affecting the pupil’s ability to constrict.

Horner’s Syndrome is also a consideration. On top of the anisocoria, cats will have a protrusion of the third eyelid and a sunken eyeball. This disease is most often idiopathic, meaning we do not find an underlying cause.

So, is it normal if my senior cat has dilated pupils?

tiger cat with dilated eyes

While it is true many senior cats develop iris atrophy with age and will have dilated pupils, we shouldn’t brush off their dilated pupils and assume it is normal.

Older cats are prone to those underlying diseases which can dilate the pupils (many of which are age-related conditions), such as an overactive thyroid gland and an increase in blood pressure.

It is important a senior kitty has a full check over if their pupils remain permanently dilated.

FAQs

tortoiseshell cat looking somewhere with dilated pupils

Dilated pupils can be a normal response to an event (such as being in a darkened room) or might be indicative of a health issue. If the pupils remain dilated for a prolonged period of time, even in bright light, there could well be a problem. A vet visit is advised, to determine what is going on with your cat’s eyes and provide timely veterinary treatment.

Yes, it is common for a cat’s pupils to dilate when in pain. Similarly, when their cortisol (stress hormone) is elevated, their pupils will be much larger than usual.

If your cat’s eyes are remaining dilated or are dilated in situations when they shouldn’t be, a vet visit is sensible. This is true regardless of your cat’s age or breed.

Conclusion

Healthy eyes will constrict and dilate, depending on external and internal factors. It is a good sign when your cat is able to do this. However, if you notice your cat’s eyes are always dilated, it is time to book a vet exam.

As there are many potential causes for pupil dilation, it is likely your vet will run a series of tests to get to the bottom of things. While some conditions can be easily treated, others have a poorer prognosis.

References

  • “APA PsycNet.” 2021. Apa.org. 2021. https://psycnet.apa.org/record/1944-00449-001.
  • “Mydriasis – an Overview | ScienceDirect Topics.” n.d. Www.sciencedirect.com. Accessed September 14, 2021. https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/mydriasis.
  • Parker, Richard. 2021. “Why Are My Cat’s Eyes Dilated All the Time? (Cat Pupil Dilation Meaning).” Senior Cat Wellness. Senior Cat Wellness. February 6, 2021. https://www.seniorcatwellness.com/cats-eyes-dilated-all-the-time/.
  • Zwueste, Danielle M, and Bruce H Grahn. 2019. “A Review of Horner’s Syndrome in Small Animals.” The Canadian Veterinary Journal = La Revue Veterinaire Canadienne 60 (1): 81–88. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6294019/.
a cute bombay cat with dilated eyes

Have you seen your cat’s eyes always dilated? Please share with us below!

Dr. Linda Simon MVB MRCVS is a locum veterinary surgeon who has worked in London for the past 8 years. She graduated top of her class in small animal medicine from UCD, Dublin. She is currently a member of the Royal College of Veterinary Surgeons.
Linda is the resident vet for Woman magazine and a frequent contributor to People’s Friend Magazine, the Dogzone website, Vet Help Direct and Wag! Linda also writes content for the CVS veterinary group, Vetwriter and a number of other establishments.

As well as working in clinic, Linda is an online vet for www. JustAnswer.com where she has been providing online advice for thousands of owners since 2018.

In her spare time, Linda enjoys baking, yoga and running around after her young son!

READ HER LATEST ARTICLES. FIND HER ON: INSTAGRAM.

Learn more about Linda here

Why Does My Eye Doctor Dilate My Eyes?

18-08-2021 · Because most eye conditions are painless, having dilated eyes can help your eye doctor diagnose such common eye diseases as: Glaucoma Cataracts Age-related macular degeneration Diabetic retinopathy These are all conditions that can lead to blindness if not treated as early as possible. What to Expect After Your Eye Dilation

18-08-2021

dilated-eyes

As part of your eye exam, your doctor may ask to dilate your eyes. Eye dilation is performed so that your eye doctor can better see inside your eye to check for problems that could affect your vision. Here are a few things you should know about why dilated eyes are often a part of a comprehensive eye exam.

Why You May Need Dilated Eyes

If you are in good health and are at low risk for eye disease, your doctor may not request to dilate the pupils in your eyes each time you have your annual eye exam. How often you will need dilated eyes typically depends on your risk for developing eye disease.

You should have a dilated eye exam every one to two years if you:

  • Are 60 years old or older
  • Have a family history of glaucoma
  • Are over 40 and African American
  • Have diabetes or high blood pressure

If you have any of these risk factors, you should let your eye doctor know. The earlier eye disease is detected, the better your outcome will usually be.

What Problems Can Be Detected During Eye Dilation

While your eyes are dilated, your doctor can see issues in your eye that would otherwise go unnoticed until they progressed to a more advanced stage and damage increases. For example, your eye doctor may be able to see problems like an eye tumor or detached or torn retina that you might not be aware of until it affects your vision.

Because most eye conditions are painless, having dilated eyes can help your eye doctor diagnose such common eye diseases as:

  • Glaucoma
  • Cataracts
  • Age-related macular degeneration
  • Diabetic retinopathy

These are all conditions that can lead to blindness if not treated as early as possible.

What to Expect After Your Eye Dilation

After your eye doctor puts dilation drops in your eyes, it could take up to 30 minutes for your pupils to open fully. Your eyes will usually return to normal within four to six hours. During this time your eyes will be more sensitive to light. It may also be difficult for you to drive after your eye exam. Therefore, unless you have not had an issue before with driving after eye dilation, it might be wise to arrange for a ride home after your exam.

Do you have questions about dilating your eyes during your eye exam? Don’t hesitate to ask your eye doctor at Valley Eyecare Center during your exam. Call us at (602) 955-2700 with questions or to schedule your next eye exam.

theanimaltypes.com

7 Why Are My Dog's Pupils So Big? 8 Eyes – Pupils Dilated – Dog Body Language – Silent … 9 Why Do Dog Pupils Get Big When Playing? 10 What causes dilated eyes in dogs? – Quora; 11 Do dogs' pupils dilate when they look at people they love like … 12 Progressive Retinal Atrophy and Iris Atrophy in Dogs – Rex … 13 Unequal Pupil Size ...

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When a dog is feeling tense, his eyes may appear rounder than normal, or they may show a lot of white around the outside (sometimes known as a "whale eye".) Dilated pupils can also be a sign of fear or arousal—these can make the eyes look "glassy," indicating that a dog is feeling threatened, stressed or frightened.

Do dogs eyes dilate when they are in pain?

In low light, your pupils open up, or dilate, to let in more light. When it's bright, they get smaller, or constrict, to let in less light. Sometimes your pupils can dilate without any change in the light. The medical term for it is mydriasis.

Do dogs pupils dilate when they see someone they love?

When pain is present somewhere in the body, your dog's pupils may dilate. If there is pain in your dog's eye, specifically, your dog may squint, and pupils may be either dilated or constricted.

How large should a dog’s pupils be?

This was backed by their emotional response, which was also altered. Without the hormone, they responded emotionally more to angry faces u2014 their pupils dilated more u2014 while when they were under the influence of oxytocin, they responded more to smiling faces.

bikehike.org

05-12-2021 · Dilation of pupils can occur in low light conditions to assist with vision by allowing more light into the eyes. In other instances it occurs as an involuntary response due to the sympathetic nervous system being activated.

05-12-2021

In low lighting conditions, your dog’s pupils dilate or get bigger so to let more light in. Their pupils will constrict, or get smaller so to let in less light. If your dog’s pupils are therefore dilated in a dark room, that’s totally normal. It’s a sign that your dog’s pupils are working properly.

What do dilated eyes indicate?

In low light, your pupils open up, or dilate, to let in more light. When it’s bright, they get smaller, or constrict, to let in less light. Sometimes your pupils can dilate without any change in the light. The medical term for it is mydriasis.

Do dogs eyes dilate when they are in pain?

Often pain elsewhere in the body will result in larger (dilated) pupils, while pain in the eye(s) can result in either larger or smaller (constricted) pupils – depending on the underlying injury or disease process, and whether one or both eyes are affected.

Does dilated pupils mean death?

Dilated pupils – is not a sign of irrevesible brain death.

When should I be concerned about dilated pupils?

If you or someone else notices you have dilated pupils or one of your pupils looks larger than the other after head trauma, seek medical attention immediately. The same is true if you experience sudden dizziness, headache, confusion, balance problems or other symptoms of a possible stroke.

Why do my dogs pupils get so big when he looks at me?

Dilation of pupils can occur in low light conditions to assist with vision by allowing more light into the eyes. In other instances it occurs as an involuntary response due to the sympathetic nervous system being activated. Dilated pupils can indicate the dog is feeling some form of stress*, fear or arousal.

Is anisocoria serious in dogs?

If anisocoria occurs suddenly, you should consider this an emergency and seek veterinary care immediately to lessen the chance that your dog’s vision will be permanently affected.

What are the signs your dog is dying?

How Do I Know When My Dog is Dying? Loss of coordination. Loss of appetite. No longer drinking water. Lack of desire to move or a lack of enjoyment in things they once enjoyed. Extreme fatigue. Vomiting or incontinence. Muscle twitching. Confusion.

Do pupils dilate during a stroke?

No significant differences were found in pupil dilation between healthy controls and individuals with stroke.

Do pupils dilate in coma?

The presence of fixed dilated pupils in a comatose patient is generally considered to be an ominous sign if reversible causes of coma have been excluded.

What does it mean if pupils are fixed and dilated?

Doctors sometimes refer to more pronounced mydriasis, when the pupils are fixed and dilated, as “blown pupil.” This condition can be a symptom of an injury to the brain from physical trauma or a stroke. The opposite of mydriasis is called miosis and is when the iris constricts to cause very small or pinpoint pupils.

Can stress cause dilated pupils?

Stimulation of the autonomic nervous system’s sympathetic branch, known for triggering “fight or flight” responses when the body is under stress, induces pupil dilation.

Can anxiety cause dilated pupils?

For example, during anxiety episodes, your body receives a rush of adrenaline. That adrenaline prepares your body to fight or flee, and one of the ways it does that is by dilating your pupils. Other changes include tightened muscles, an increased heart-rate and increased blood flow to your peripheries.

Are dilated pupils normal?

Dilation, or widening, of the pupils of the eyes is normal in conditions of low light in order to allow more light to reach the retina. Medically, dilation of the pupils is known as mydriasis. Specific medications known as mydriatics are administered to dilate the pupils for ophthalmologic examination.

How do you tell if your dog loves you?

How can you tell if your dog loves you? Your dog is happy to see you. Your dog gives you presents. Your dog puts you second only to food. Your dog likes to sleep with you. Your dog looks at you with loving eyes. Your dog does not care about your appearance. Your dog follows you everywhere.

Do dogs pupils dilate when they look at something they love?

This was backed by their emotional response, which was also altered. Without the hormone, they responded emotionally more to angry faces — their pupils dilated more — while when they were under the influence of oxytocin, they responded more to smiling faces.

Why do dogs look at you while they poop?

Eye Contact You’d think she’d look away in hopes of getting a little privacy, but she locks eyes with you instead. That’s because when your dog is in that pooping position, she’s vulnerable, and she’s looking to you to protect her. “Your dog is instinctively aware of his defenselessness.

Can anisocoria in dogs go away?

Treating Your Dog’s Anisocoria Some causes, such as Horner’s Syndrome, are self-limiting and the anisocoria may resolve on it’s own. For still other causes, such as degenerative conditions, your dog’s anisocoria may never get better. Some causes of anisocoria may also require long term medication.

Does anisocoria affect vision in dogs?

Symptoms of Anisocoria in Dogs Anisocoria is a symptom, and its presence signals a medical issue. If anisocoria suddenly occurs in your dog, seek medical help immediately, as it could be a sign of a serious and progressive condition which could cause your dog’s vision to be permanently affected.

Will anisocoria go away?

Simple anisocoria This is a benign condition that causes the pupils to differ in size, usually by up to one millimeter in diameter, without affecting the pupils’ response to light. This condition can be intermittent or constant, and may even go away on its own without medical intervention.

How do I tell my dog goodbye?

Making the Final Choice If there is time, spend a few moments just talking to your dog. It may sound strange to some people, but a pet can pick up a lot from the tone of your voice. Plus, saying things out loud might help you process things. Try to allow time for family members to say their goodbyes as well.

What happens right before dog dies?

Dogs can show a variety of behavioral changes when they are dying. The exact changes will vary from dog to dog, but the key is that they are changes. Some dogs will become restless, wandering the house and seeming unable to settle or get comfortable. Others will be abnormally still and may even be unresponsive.

Why is my dog disoriented and walking in circles?

Vestibular ataxia is the result of an issue with the inner ear or brainstem. Along with staggering, stumbling and falling over, signs of ataxia include head tilt, walking in circles, vomiting, nausea, and flicking of the eyes from side to side.

Why Are My Eyes Dilated?

Dilation is when mydriatic drops are placed in the eye. The mydriatic drop is an agent that induces dilation or enlargement of the pupil. Drugs such as tropicamide are used to permit examination of the retina and other structures of the eye, and also to reduce painful ciliary muscle spasms.

Throughout any normal day, we see many emergency office visits. One recently peaked my interest – a patient called and said she thought her cat scratched her eye. Her eye was tearing profusely and light sensitive, but her biggest concern was her dilated pupil. This young lady had rinsed her eye with some over the counter allergy drops, and after 10 to 15 minutes she noticed her pupil was very dilated.

First, let’s define dilation. It is a common term used in the eye field. But there are many new techs out there that may not know the distinctions of the word. Dilation is when mydriatic drops are placed in the eye. The mydriatic drop is an agent that induces dilation or enlargement of the pupil. Drugs such as tropicamide are used to permit examination of the retina and other structures of the eye, and also to reduce painful ciliary muscle spasms. Once the drops are placed in the eye, it takes about 15 to 20 minutes to fully dilate the pupil. The dilating eye drop may make the eye sting and may also cause a medicine taste in the mouth. Common side effects are blurry near vision and light sensitivity - sometimes for several hours.


Dilated pupil on left. Constricted pupil on right.

Most over the counter drops are phenylephrine. This is a decongestant that shrinks blood vessels. Phenylephrine ophthalmic is used to relieve eye redness, dryness, burning, and irritation caused by wind, sun and other irritants. Prescription-strength phenylephrine ophthalmic is used to constrict blood vessels in the eye and dilate the pupil for conditions such as glaucoma, before surgery, and before eye examinations.

Phenylephrine has many side effects in addition to pupil dilation. It can cause rapid heartbeat, sweating, tremors, pale skin, light headedness, severe headaches, buzzing in ears, anxiety, shortness of breath, chest pain or pressure, and pain in the jaw that can spread to your shoulder. Although the risk of serious side effects is low when phenylephrine ophthalmic is used in the eye, these side effects can occur if the medicine is absorbed into the bloodstream.

A bigger concern is the possibility of inducing narrow-angle glaucoma by using the wrong eye drop or medication. Acute narrow-angle glaucoma can occur suddenly when the iris is pushed or pulled forward. This is exactly what happens to the iris when the pupil is dilated. The angle-closure causes blockage of the drainage angle in the eye, where the trabecular meshwork allows outflows of fluids. When the internal eye structure is blocked in this way, the intraocular pressure of the eye may spike. The pressure spike can damage the optic nerve (the optic nerve is the nerve that transmits the images from the eye to the brain). Angle-closure can cause severe eye pain, headaches, halos around lights, nausea and vomiting, and even vision loss. Acute angle-closure glaucoma is a medical emergency. If the high pressure is not reduced quickly, it can cause permanent vision loss.

During a routine vision exam, your eye doctor will check the angles to make sure the patient is safe for dilation. But when a patient is self treating with over the counter medications the angles are not being evaluated and even though it is rare; angle closure is possible. Before using drops that contain phenylephrine, make sure you get approval for use from your eye doctor. The doctor may also have recommendations that will produce a better result depending on the problem. If a patient is having symptoms of an eye infection or abrasion, the doctor will instead prescribe an antibiotic. This was the case for the patient that came into the office with the cat scratched cornea. She was given an antibiotic drop and a bandage contact lens. She was advised to stop using the over the counter drop. Within one day, her corneal abrasion was healed, and the pupil returned to its normal size.

Linda Hardy received the American Optometric Association Paraoptometric of the Year Award at the 2016 SECO meeting in Atlanta, Georgia. Linda is a Certified Optometric Technician (COT) and Certified Ophthalmic Assistant (COA). She is also ABO and NCLE certified and a Licensed Dispensing Optician (LDO) in the state of Georgia.

A graduate of Georgia Medical Institute as a Registered/ Certified Medical Assistant, Linda began her optical career working with a group of ophthalmologists as an ophthalmic assistant. She has been the Clinical Coordinator with a private optometry practice in Newnan, Georgia for 15 years.

Linda is also a speaker and educator at regional optical meetings. She and her husband have five children, and she enjoys spending time with her family, exercising, reading and volunteering in her community.

ikittycat.com

05-08-2021 · What if only one eye of my cat suffers from dilation? This question is much confusing than why are cat’s eyes are always dilated. A mismatched cat pupil size means that your cat’s pupils are not the same. It may have several reasons behind it for the real cause. Permanent dilation of one eye is more common, so your cat can keep one eye closed. [H2]Common reasons include: Physical trauma ...

05-08-2021

Cat’s eyes are one of the most beautiful eyes to see in the entire animal kingdom. And feline lovers are fortunate enough to have the privilege to look at these cuties whenever they like. But have you ever thought about what is so different about the cat’s eyes?

It is amazing to experience that cat pupil are a potential source to show how your cat is feeling — emotionally and physically. A tiny and slow blink is enough to show that your cat means to say “I love you”. But that is not enough, there can be a lot of other factors attached to it i.e., pupil dilation.

Cat’s Pupil Dilation

Cats usually dilate their pupils to improve vision. The wide and broad eyes allow cats to absorb more light, which helps in low light.

When a cat gets excited, scared, or injured, its pupils also dilate simultaneously. And it won’t last long.

Usual changes in pupil size and response to different conditions are completely normal. There is nothing to worry about, but it does promote a healthy eye function, allowing your cat to have better eyesight in different light conditions and a natural response to emotion or fear.

But if you see it continuously, and you ask yourself why are my cat’s eyes always dilated, there could be a chain of multiple possible signs. It could be because of age-related pain, over-irritation, or atrophy.

The cat’s eyes need to be dilated regularly, so if the pupils never contract, this is a real problem. So, note down all the observations carefully.

What are the Common Reasons for Pupil Dilation in a Cat?

Reason #1: Better vision

The expansion and contraction of a cat’s pupils are directly proportional to the level of light. In bright light, it mostly shrinks to protect the major part of the eye and in the dark it expands as much as it could.

If you want to know that cats can see things in the dark, its sight is not perfect and it can’t see what we see in the dark. However, it can see better in low light conditions, thanks to the dilated pupils and letting as much light into its eyes as possible.

Due to the way your cat’s pupils respond to light, your vet will generally use a bright light to assess his eye function. If you shine a flashlight on your cat’s expanded eyes and it don’t shrink, you know there is a potential problem.  Otherwise, it’s just due to better vision.

Reason # 2: Surprise or fear

If you’re panicking again that why are my cat’s eyes always dilated?

Always remember, a cat’s eyes get widen when it is surprised or frightened. It’s a natural phenomenon.

When a cat gets scared, it produces a hormone named adrenaline, which promotes the rate of survival in it. This surge in adrenaline makes them feel braver, but here’s one thing more.

It also makes changes in its bodies, such as increasing the heart rate and pumping more blood to its muscles, heart, and lungs, preparing to escape difficulties or prepare for battle.

So if your cat’s pupils are large and round, it’s best to leave it alone. It can be any noise that scares your cat, from loud noises to unfamiliar visitors, so please give it some time to settle down and realize that it is still in a safe space and approach it when its eyes return to normal.

Reason #3: Excitement

If the cat’s eyes enlarge when it’s playing – it’s pretty confusing. Is it afraid of the cat toys or you?

This question often confuses the caretaker, but dilated pupils may also be a sign of excitement. However, you can easily distinguish the difference between the two by observing the surrounding environment.

If you are playing with your cat or just giving it snacks, you can safely assume that its pupils are dilated due to excitement. However, if it hides under your sofa in a storm, it may be scared.

Here is the same reason again as mentioned above, that cat’s eyes dilate while playing is the adrenaline is pumped through their bodies again. How we play games with cats is the same as what these animals do hunting in the wild. It needs to be alert, fearless, and have enough blood in its muscles so that it can react quickly and grab the next meal, and for this, it rely on adrenaline.  So, here it connects the two of it like playing with toy mice, chasing ropes, or kicking cat toys at it. Therefore, when it play, an adrenaline rush hits them.

But, what if your cat’s eyes are always widened?

If your cat’s pupils dilate periodically and the light around her changes, this is normal, and there is no need to worry. Your cat may suffer from it having its tail stepped on or by a loud noise.

Like there’s also another reason that the brighter the light, the clearer cats can see. According to research, cat pupils are 10 times larger than human pupils. If the light is bright enough, most probably the cat may dilate its pupils for multiple reasons. And at night, it’s usually due to darkness. And we assume this to be a massive problem.

Only when you notice that your cat’s pupils are dilating all the time, you should worry about it and check it to make sure your cat’s eyes are healthy.

One of the most common reasons behind it is Continuous expansion. It is usually a sign of high blood pressure, but it may also indicate that they are blind, experiencing chronic pain, or have other underlying health conditions.

Some other medical or psychological reasons include Shock, Excitement, Pain, Unwellness, Eye trauma, etc.

My cat’s eyes keep dilating more often – Why?

Mostly cat’s eyes should remain neutral most of the day. Due to medical or psychological reasons, the cat’s eyes may remain dilated during the day and night. Common explanations include:

  • Blindness
  • Stress & Anxiety
  • Overexcitement
  • Chronic Pain/ Disease
  • Intake of Toxins
  • High Blood Pressure
  • Dysautonomia
  • Iris Atrophy
  • Ocular Cancers and Tumors
  • Eye infections and diseases
  • Feline Leukemia Syndrome (FeLV)

Let’s discuss them one by one.

1.BlindnessSigns of cat's blindness leading to dilation
It can be temporary or permanent. In addition to expanding pupils, signs of cat blindness include: • Clumsy and collision with unfamiliar objects. • Scared while jumping or climbing • Getting frightened randomly with the sudden attacking noises • Facing difficulty in judging and locating the water source. • An excessive pitch of voice, and increasing pain when not responding.
How to deal with this situation?
Don't panic. Compared to sight, cats rely more on smell, hearing, and touch. Make some rearrangements in your home to make it easier for your cat to roam around, so it can quickly adapt itself to poor or no vision. You should provide unobstructed access to food, water, and garbage. Kick your presence when entering the room. Talk to your cat regularly because your voice will provide comfort.
Pro Tip: A simple test to test if your cat’s vision leading to dilation
Shake a ball of yarn in front of the cat’s eyes. Don't swing the yarn very close to the cat’s face as the cat may feel it. If your cat can see properly, its hunting instinct will start working. It’s evident that a blind cat will behave differently. Moreover, if your cat has completely lost its vision, it will learn to cope.
2.Stress and AnxietyWhat to do if you notice that your cat is suffering from stress and anxiety/ exhibits other symptoms of stress?
Another reason for the dilation in some cats is that they are scared because when they feel anxious, worried, or hear a sudden loud noise, their eyes will naturally expand. Continued high stress can cause several other problems, including aggression or loss of appetite.It's important to take the following steps to eradicate and treat dilation in cat's pupils • Try to find out the core reason, like any new changes in your daily life. Plus, are there any new people or animals in your family? Make necessary adjustments accordingly. • You can try to bring your cat to a new environment to make him more comfortable. In addition, be sure to add a lot of hiding places for your cat at home, such as cat carts or cardboard boxes. If your cat is stressed and needs some time, this provides a place to retreat. • If your cat already behaves nervously, medication can help them calm and relax. If the treatment is effective, you will notice that the cat’s pupils shrink. • Maintain a strict and proper schedule for daily activities to keep your cat busy, happy, and contented.
3.OverexcitementReasons of Overexcitement
If nervousness or being scared isn’t the reason for your cat’s pupil dilation - it may just be overexcitement. • Cats get excited about numerous reasons. If you don't calm them down, they may become overly excited. It may result in extra pressure on their heart. • When a cat is in a new environment, overexcitement is common.
How to treat it?
For some days guide him to a separate room. Once the cat returns to its normal state, its pupils will be ok.
4.Chronic pain/ diseaseSymptoms of eye dilation due to chronic pain
One of the most common reasons for pupil dilation in a cat is chronic pain. Cats try to hide their pain intentionally. It is because vulnerability in the wild will make them a target for predators. • Cat loses its appetite. • It behaves more aggressively or tiredly than usual. • It loses interest in self-grooming. • It may be suffering from arthritis or dental problems.
Treatment
For the best advice, consult a vet. Then they will be able to diagnose what is causing your cat's continued discomfort. Cats can hide their body pain very well, but not all the time. The expanding cat's eyes are clues. If your cat's eyes are wide open, look for other symptoms as mentioned above.
5.Intake of toxinsSymptoms of dilation through intake of toxins
It leads to dilated eyes in cats. Cats that eat toxins will have enlarged eyes.It may include the following risks: • Vomiting and diarrhea • Difficulty breathing • Weakness and lethargy • Muscle tremors • Low body temperature • Lethargy • Loss of appetite Most of the household products contain toxic. When your cat ingests toxins, it needs to get rid of them from the body.
6.High Blood pressureSymptoms of High Blood pressure
160/80 mmHg, is considered to be high blood pressure in cats. Older cats suffer more of it. And it can easily be recognized through the pain lying in their eyes resulting in dilation.Hypertension or high blood pressure doesn't come suddenly. Other health problems like kidney issues or heart problems are relevant with it. Other symptoms related to it include Excessive alcohol consumption, Blood in urine, Nosebleed.
How to treat it?
It may be hard for vets to diagnose hypertension and abnormalities in cats’ imaginative being. In that case, consulting an experienced vet is the only prescribed solution.
7.DysautonomiaSymptoms of Dysautonomia
Dysautonomia, additionally referred to as Key-Gaskell Syndrome or Feline Dilated Pupil Syndrome assaults a cat’s automatic nervous machine (ANS). • Digestive problems • Lack of appetite • Unusual weight loss • The constant urge for food • Slow heart rate • Dry nose • Low body temperature • Not being to urinate or defecate • Enlarged esophagus • Swollen abdomen
Treatment
You must take your cat to the vet immediately if you see any of these symptoms. In most cases, the cats don't survive with these symptoms and usually, only the medication is provided. It takes almost a year to recover fully, and many of the times permanent dysfunctionality remains at its place.
8.Iris AtrophyAfter-effects of Iris Atrophy
It's a common phenomenon in most cats that their iris starts getting thin as the cat grows older and results in dilation.Its permanent damage that’s why it’s irreversible, but it will not suffer any pain in this. Some major changes after it include sensitivity to luminous light, though. Moreover, it will squint and hide in dark corners, so better to avoid it.
9.Ocular Cancers and TumorsSymptoms of Ocular Cancers and Tumors
A malignant tumor is developed at the back of the cat’s eye sometimes. It can spread to other parts of the body as well and it’s extremely painful for the cat, leading to dilated pupils. • Discoloration • Inflammation • Glaucoma • Irregular discharge from the eye • Misshapen iris • Cloudy eyes
Treatment
The diagnosis of eye tumors is not an easy task, but an ophthalmoscope is used. Moreover, Biopsies are done to judge its severity. If the tumor is small, the laser is used to treat it. Or if the case is worse than this, full removal of the eye will be needed to prevent the tumor from spreading.
10.Eye infections and diseasesTreatment of Eye infections and diseases
Cats easily get caught with severe eye infections and diseases. It may have several reasons behind it like bacteria, irritation, or allergies.Simple eye infections can be treated with some dosage of antibacterial eye drops. If it works then, your cat's eyes will return to their original size.
11.Feline Leukemia Syndrome (FeLV)Symptoms of (FeLV)
This condition can cause the irregular corners of the eyes to move from one eye to the other. If the change in an uneven eye pattern is notice regularly, the cat most probably is suffering from FeLV. It’s an infectious disease that can easily be transmitted through blood, saliva, or waste. Many of the times, its severe causes can lead to death. FeLV vaccine is a must for all adult kittens and cats. • High fever • Shortness of breath • Loss of appetite and weight loss • Pale gums • Infertility • Lethargy • Poor hair quality
Treatment
FeLV cannot be cured, so vaccination is essential. It’s better to keep the cat indoors in such a case. It is because Co-breeding is a risky option to have here as the infected cat again catches the virus.

What if only one eye of my cat suffers from dilation?

This question is much confusing than why are cat’s eyes are always dilated. A mismatched cat pupil size means that your cat’s pupils are not the same. It may have several reasons behind it for the real cause. Permanent dilation of one eye is more common, so your cat can keep one eye closed. [H2]Common reasons include:

  • Physical trauma
  • Glaucoma
  • Corneal ulcer
  • Ectopic disease – common in old cats
  • Anisocoria

Like double pupils, uneven eye corners are a long-term condition. In contrast, trauma, like a punctured eye, can cause a temporary disparity in the pupil. If heterotopic pupils last longer than 24 hours, your cat should be checked by a veterinarian.

Final Words

Pupils that dilate and constrict in every other situation is a healthy sign, but if it remains permanent then it can be concerning. It is best to judge the cats’ eyes often as it says a lot about how your cat is feeling and maybe you can judge the underlying conditions from it.

Go to your vet at first if you notice your cat has permanently dilated pupils. Only a vet can diagnose the underlying problem and provide effective treatment for it. Other conditions could also be the culprit, and you can manage the majority of it with the correct treatment.

The most important thing to remember is not to panic. Follow the advice of your vet and your cat will likely be well and back to normal in no time at all.

We Dilate Patients' Eyes in Order to Clearly View their ...

The retina’s job is to detect light and report that nerve signal to the brain in order for the brain to generate the perception of vision. The retina is a thin membrane that is vulnerable to many different eye diseases. Without having the eyes dilated and viewing the retinas, eye disease may go undiagnosed and lead to serious visual consequences including blindness.

This image shows an image of a retina with a multitude of diseases.

Why do you dilate patient’s eyes?

Part of every patients’ annual comprehensive eye and vision examination is checking the health of the back of the eyes. The retina’s job is to detect light and report that nerve signal to the brain in order for the brain to generate the perception of vision. The retina is a thin membrane that is vulnerable to many different eye diseases. Without having the eyes dilated and viewing the retinas, eye disease may go undiagnosed and lead to serious visual consequences including blindness.

What are the side effects of eye dilation?

The biggest side effects of having your eyes dilated is that you will have light sensitivity and blurred near vision for 2-4 hours after the procedure. Most patients are perfectly fine to return to work as long as they are not driving or using heavy machinery. If there is any concern with your ability to work or drive safely, you are welcome to return another time to have your eyes dilated.

Do you charge to performed a dilated retinal examination of a patient’s eyes?

If the eye dilation is part of a patient’s annual comprehensive eye and vision examination, we do not charge to dilate the eyes. If your visit is a medical visit rather than your annual eye check-up, we would bill either your medical insurance or the patient for that visit.

Can I return and have my eyes dilated another time?

If you are unable to stay at the time of your annual comprehensive eye and vision examination for your dilated retinal examination, you are welcomed to return within the next 30 days to have your eyes checked at no charge.

Can I drive with dilated eyes?

We recommend you bring a driver with you to your eye exam so that you don’t have to worry about driving with compromised vision.

Who do you recommend get their eyes dilated?

Our doctors generally dilate all new patients of all ages. Patients with a history of high myopia, diabetes, hypertension, cataracts, existing retinal disease, family history of retinal disease, history hydroxychloroquine (Plaquenil) use, or certain eye or vision symptoms, should have their eyes dilated at each year’s annual appointment.

What diseases do your eye doctors look for when viewing the retina in dilated eyes?

Through the dilated pupils, our eye doctors are better able to assess cataracts, optic nerve health (looking for signs of glaucoma or optic neuritis), macular health, blood vessel health, vitreous, and peripheral retinal health including looking for retinal holes, retinal tears, lattice degeneration, and retinal detachments.

Do I have to get my eyes dilated?

Our doctors highly recommend viewing the retinas through dilated pupils as doing so allows us to best manage your eye health. As vision is the most precious of our senses, we strongly recommend checking your eye health which is part of your annual comprehensive eye and vision examination. If you decline both OPTOS imaging, and having your eyes dilated, you are not allowing us to view your retina health. Patients of all ages can suffer from eye disease that can only be detected by viewing the structures at the back of the eyes. If you decline both OPTOS imaging and having your eyes dilated, we ask that you please complete a medical waiver stating that we educated you on the importance of checking your eye health and that you nevertheless declined this part of your eye exam.

Do you dilate children’s eyes?

Because eye disease can occur at any age, we do indeed dilate children’s eyes. The eye drops don’t hurt, and children typically tolerate the side effects very well. Sometimes a stronger dilating drop (a “cycloplegic” drop) is used to better assess the glasses prescription of younger patients. We use these cycloplegic drops in patients aged 6 months to about 10 years. The blurred vision and light sensitivity that result from these cycloplegic drops can last as long as 24 hours. While the side effects are noticed for a longer period of time, the benefits of being able to accurately determine a child’s glasses prescription, and the ability to check the health of the back of their eyes, make this procedure well worth the minor inconvenience.

Can I do OPTOS imaging instead of having my eyes dilated?

OPTOS imaging is a great way to view the back of the eyes. It provides our doctors with a panoramic view of your retinas known as an “optomap®.” To be thorough, we recommend that patients have both optomap® imaging of their retinas, as well as a through, dilated eye examination. The optomap® gives our doctors detail and allows us to accurately record the appearance of any retinal findings, though actually dilating the eyes gives our doctors stereoscopic views, better color accuracy, and a larger view area of the retina. We regard OPTOS as the next best thing to having your eye dilated, but OPTOS is not a substitution for a dilated retinal examination.

Can I have my eyes dilated if I am pregnant?

If there is a pressing need to view the retinas in a patient that is expecting, we will absolutely dilate your eyes. However, in the absence of high risk factors and symptoms, we recommend that expecting mothers sit for OPTOS imaging while they are pregnant rather than have their eyes dilated. They are encouraged to return for their dilated fundus examinations after delivering their child.

Which patients are most at risk for retinal disease?

Patients with high myopia (nearsightedness), diabetes, hypertension, high cholesterol, family history of retinal disease, patients using certain systemic medications, and patients with a history of trauma. While these are indeed risk factors, it is important to note that any patient of any age can suffer retinal disease that is always better treated when identified early.

Please call us today at (303) 450-2020 to schedule your annual comprehensive eye and vision examination, or use the button below to schedule your exam online:

Why Are My Cat’s Eyes Dilatated?

Anisocoria, characterized by one enlarged and constricted pupil, is another cause for detecting a dilated pupil. In various health problems, the pupils may appear uneven, with one pupil more significant than the other. Make an appointment ASAP with your vet to evaluate and analyze your cat’s vision if you notice this in them. Anisocoria can get caused by several things, ranging from Glaucoma ...

To increase their vision, cats widen their pupils. Felines with large eyes can embody more light, which is advantageous in low-light situations. When furballs are agitated, terrified, or harmed, their pupils dilate. It should never go on for more than a few hours.

Overstimulation, age-related atrophy, or pain can all cause cats’ eyes to dilate constantly. Dilated pupils have gotten linked to Dysautonomia, toxicity, tumors, feline leukemia, and other health issues.

Cats’ pupils should dilate and constrict regularly. Thus it’s a severe problem if they never do. Your cat’s eyesight may get jeopardized if this occurs. Maintaining excellent furball eye health begins with correctly diagnosing and treating the problem.

Why Are My Cat’s Eyes Dilatated?

In the dim light, cats frequently expand their eyes to view clearly. Cats’ pupils allow light to enter their eyes, and the more daylight they have, the better they can see. As a result, a cat’s pupils may appear to be perpetually dilated at night.

Cats’ pupils can extend up to ten times broader than humans’. Mydriasis is the medical term for dilated pupils. A cat’s pupils will enlarge for a specific reason if the lighting is not dim. These are some of them:

· Perplexed or startled

· Thrilled

· discomfort

· I’m sick

· Trauma to the eyes

It’s not a big deal if the dilatation is only transitory. Someone may have walked on your cat’s tail, causing it agony. Similarly, if your furball is frightened by a heavy noise, it will rapidly recover.

My Cat’s Pupils Are Permanently Dilated:

For most of the day, cats’ eyes should be in an indeterminate state. Extension of the pupils should be uncommon rather than the rule.

For medical or psychological reasons, cats’ eyes may remain dilated throughout the night and day. The following are some examples of common explanations:

· Deafness

· Anxiety disorder

· Excessive stimulation

· Persistent or chronic discomfort

· Toxic substance use

· High blood pressure

· Dysautonomia

· Medication side effects

· Iris atrophy due to old age

· Tumors of the eye

A cat’s eyes will persist dilated at all times if it is losing its vision. The kitty is seeking to assimilate much light to enhance its image. Senior cats, especially purebred cats, frequently begin to lose their vision. The blindness may be permanent or temporary. Apart from permanently dilated pupils, there are other symptoms that a feline starts going blind:

· Clumsiness and colliding with strange items.

· Walking with low-hanging whiskers.

· Nervousness when jumping or climbing.

· Afraid of being startled by loud noises.

· Finding a source of water is difficult.

· Excessive vocalization, which becomes agitated if you do not answer.

In front of the cat’s eyes, hail a wool ball. Swing the thread too close for the cat’s whiskers to detect it. Your cat’s hunting abilities will get triggered if it can see. Of course, a blind feline will be unconcerned.

Your cat’s blindness may be only temporary. Short-term blindness can be caused by kidney problems, poisoning, feline herpes virus, and eye contaminations.

If your furry friend loses its sight permanently, it will begin to cope. Eyesight is often regarded as a cat’s least helpful sense. Hearing, scent, and touch are more important to cats. The following suggestions will assist you:

· Make no changes to the furniture.

· Ensure there are no impediments in the way of food, drink, or trash.

· Stamp your feet to advertise your presence.

· Talk to your feline daily to provide comfort.

· Stay away from loud, unexpected noises.

When a kit feels scared, its eyes remain dilated and wide. A kitty with stress will have dilated pupils all of the time. You’ll need to figure out what’s causing your cat’s wide-eyed dread. It could be anything from a deep noise to a stranger’s presence. When alarmed, cats will frequently hide or flee. The cat’s eyes should not be dilated anymore when it emerges from its hiding place.

A cat with widened eyes appears to be on edge all of the time. The cat is terrified of danger at all times. Long durations of anxiety and stress can lead to health concerns. It’s also possible that the cat will grow more aggressive.

Determine the source of the cat’s stress and make necessary modifications. Cats get frequently stressed as a result of a shift in their daily routine. To keep your cat happy and comfortable, stick to a rigid, consistent regimen. Some felines are naturally nervous. Use relaxing scents and sounds, herbal therapies, and medication to soothe your cat in these situations.

It’s possible that if a feline isn’t anxious, it’s overstimulated. Sounds, fragrances, and sights elicit excitement in cats. It will become overly stimulated if it is not calmed down, putting pressure on the heart. When a kitty gets introduced to a new environment, it is usual for it to get overstimulated. While investigating new surroundings, the cat will become agitated. If a new cat’s eyes are constantly dilated, take it to a solitary room. The cat’s pupils will return to normal once it has calmed down.

Cats are masters at concealing physical discomfort.

They can’t hide all signs of discomfort, and their perpetually dilated eyes are a dead giveaway. If your cat’s eyes are dilated, search for additional signs of distress. These are some of them:

· Aversion to food

· Laziness

· Lack of enthusiasm for grooming

· Aggression that is out of character

· Refusing to be petted or handled

Make your furball as comfortable as possible as you try to figure out what’s wrong. Arthritis is a constant threat to senior cats. Nutritional supplements, soft blankets, and massage can help with this. Painkillers on prescription will also be accessible.

If your kitty has terrible breath, it could be suffering from dental problems. Most felines will develop dental problems at some point, and dental disorders have been linked to health difficulties.

The eyes of a cat who has absorbed poisons will be dilated. Aside from eye dilatation, other toxicity warning signs include:

· Diarrhea and vomiting

· Breathing problems

· Weakness and sluggishness

· Tremors in the muscles

· Shallow body temperature

· Laziness

· Appetite suppression

Since numerous household and garden goods are poisonous, toxicity is always a possibility. You must expel toxins from your cat’s system if they have been ingested.

Hypertension is diagnosed when a feline’s blood pressure is 160/80 mmHg. Elevated blood pressure is standard in older cats. Dilated eyes can occur as a result of the discomfort and pain associated with the illness.

Hypertension is frequently a complication of another illness. It may be tied to another health issue, such as renal or cardiac issues. Other symptoms, in addition to dilated eyes, include:

· Excessive use of water

· Urine with blood

· Circulation

· Rhinitis

· Unusual heartbeat

· Tremors in the muscles

· Convulsions

A cat who takes hypertension medication will see a symptom reduction. Unfortunately, the cat’s eyes could still be dilated. 

Dysautonomia, commonly known as Key-Gaskell Syndrome or Feline Dilated Pupil Syndrome, is a condition in which a cat’s autonomic nervous system is attacked (ANS). It suggests that a cat’s primary functions are beyond its control.

Dysautonomia must immediately get addressed because it is a violent and degenerative illness. The most apparent sign is constantly widened eyes. Other issues to consider are:

· Problems with digestion

· A runny nose

· Weight reduction due to a loss of appetite

· Food regurgitation

Eyelid protrusion is a condition in which the upper eyelid protrudes beyond the upper eyelid.

· Reduced heart rate

· Shallow body temperature

· Urinary or esophageal incontinence

The most prevalent warning signals are an increased esophagus and a bulging abdomen. Keep a watch out for a wide-eyed feline that barfs or disgorges its food frequently.

The iris of an aged cat becomes too thin. Your cat’s pupils will be unable to constrict after the iris has degenerated.

Iris atrophy is permanent, although the feline will not suffer. However, it may grow sensitive to intense light. Provide an escape route from weak areas because the kitty will peek and sneak in shadowy corners.

Tumors And Cancers Of The Eye: 

A tumor that forms behind the cat’s eye is often malignant. It can develop throughout a cat’s body. As a result of the pain, your cat’s pupils will become dilated. 

· One of the other indicators is discoloration. 

· Irritation is another sign. Glaucoma is an eye condition that affects people of all ages.

· Excessive ocular discharge 

· Iris with a crooked shape 

· Hazy eyes

An eye cancer diagnosis is completed with the use of an ophthalmoscope. Biopsies will be taken to establish the tumor’s severity.

If it is small enough, laser treatment may be an option. The eye must usually get removed entirely to stop the tumor from developing.

When They’re In The Mood To Play: 

On the other hand, fear or astonishment may have the same impact. Changes brought on by excitement or worry should only be brief. The big visible pupil should reduce in size as the cat relaxes. A young active cat is significantly more likely to have wide pupils due to excitement or anxiety because they are intrinsically more curious and lively. When a cat is calm and relaxed, it is less likely to dilate its pupils in reaction to stimulation.

Pupils That Aren’t Dispersed Evenly:

Anisocoria, characterized by one enlarged and constricted pupil, is another cause for detecting a dilated pupil. In various health problems, the pupils may appear uneven, with one pupil more significant than the other. Make an appointment ASAP with your vet to evaluate and analyze your cat’s vision if you notice this in them. Anisocoria can get caused by several things, ranging from Glaucoma to nerve or brain traumas.

Why Are My Cat’s Eyes Sometimes Dilated?

On the other hand, students are expected to change their size and react to varied situations. It is not a motive for alarm but rather a sign of healthy eye function, which allows your cat to see better in different light conditions and is a natural response to being excited or afraid.

Improved Vision: 

You’ll notice that your cat’s pupils dilate and contract as the light level changes. In bright light, they constrict to protect the back of the eye but dilate in the dark to receive as much light as possible.

If you’re wondering whether cats can see in the dark, you should know that feline vision isn’t perfect, and they can’t see in the dark any better than we can. They can see far better in low-light circumstances because their pupils dilate and allow as much light into their eyes as possible.

Because of how their pupils respond to light, your vet will frequently use a solid light to examine your cat’s eye function. If doctors put a bright lamp into your cat’s dilated eye and it does not contract, they know an underlying problem.

Fear Of Bewilderment:

Cats’ eyes dilate when they are surprised or terrified. When your cat is scared, adrenaline is produced in large quantities to help them survive. It not only makes people feel brave, but it also creates physical changes in their bodies, such as raising their heart rate and delivering more blood to their muscles, heart, and lungs, which prepares them to leave or fight in a dangerous circumstance.

The dilation of the pupils of cats is another effect of adrenaline. If your cat’s pupils are large and spherical, it’s best to leave him alone. Anything from a loud noise to an unexpected house visitor can startle your cat, so allow them some time to calm down and realize they’re still safe before approaching them.

Excitement:

Why do cats’ eyes dilate when they’re playing, yet they enlarge when they’re afraid? Is it accurate to state that they are terrified of their toys? Is it true they aren’t having a good time with you?

Although dilated pupils can also be a sign of enthusiasm, owners are usually baffled by this. It is intriguing because their eyes react in the same way to two polar opposite emotions. You can see the difference between the two by looking at the surroundings.

If you’re playing with your cat or have just given them a treat, it’s safe to assume that their pupils are wide and dilated because they’re enthusiastic. If they’re hiding beneath your couch during a thunderstorm, they’re probably scared.

As cats play, adrenaline rushes through their bodies, causing their pupils to dilate. When searching for food in the wild, cats must be vigilant, courageous, and have a lot of blood circulating to their muscles, and they rely on adrenaline to help them respond quickly and get their next meal.

Our furry companions enjoy hunting, whether it’s with toy mice, chasing bits of string, or pouncing on a cat-kicking toy. As a result, adrenaline will rush through their bodies as they play, causing their pupils to dilate naturally.

Eye Diseases: 

Anisocoria is a disease that affects senior cats. Anisocoria might be a sign of a more severe problem. Some examples of typical explanations are as follows:

· Injuries to the body

· Glaucoma is an eye condition that affects people of all ages.

· Infection and disease in the eye 

· Spastic pupil syndrome in cats Corneal ulcers are a form of corneal ulcer.

Infections, Ulcers, And Eye Diseases Are All Standard:

Our little furry friends are susceptible to several ocular diseases and abnormalities, which Irritation, allergies, or germs might cause. External eye contamination can get healed with antibacterial eye drops. Your cat’s eyes will revert to their original size if you succeed. Ulcers are frequent in senior cats and can be removed with a scalpel by a veterinarian. Ulcers are unpleasant, but they are treatable. Glaucoma, for instance, is a more severe problem. Glaucoma has compressed your cat’s optic nerves. Your cat’s sight may be lost if left untreated.

Little Furballs With Spastic Pupil Syndrome:

This syndrome makes anisocoria change from one eye to the other. Spastic pupil syndrome is a common symptom of feline leukemia in cats (FeLV). When a cat’s mismatched eyes alter regularly, FeLV is virtually always present.

Feline leukemia is transmitted through saliva, feces, or blood. If the condition recurs, it might be fatal. All adult furballs and kittens are vaccinated against FeLV. Other signs and symptoms include: 

· High temperature 

· Breathing issues 

· Lack of appetite and loss of weight

· Discolored and pale gums

· Infertility 

· Laziness 

· Low-quality fur

FeLV has no cure, which is why vaccination is essential. You should confine your cat to the house if it has been diagnosed with FeLV. If the virus has once infected the cat, it may become infected again. Interacting with other felines enhances the risk of Infection.

Why Are My Cat’s Eyes Dilated?

24-01-2022 · Cat’s Eyes Dilate When Something Is Wrong If you notice any strange dilation with your cat’s eyes, it might be time to call your veterinarian. Unusual dilation could be a signal that something is going on with your kitty’s health. These pupil changes could be an indication of: Excessive stress A seizure condition A bad reaction to medications

24-01-2022

Do your cat’s eyes look really big sometimes? It means they’re dilated. We can help you understand why are your cat’s eyes are sometimes dilated.

What does it mean when your cat’s eyes look so big? Cats have many unique behaviors that keep us intoxicated with love while also scratching our heads with confusion. If you’ve ever looked into your cat’s eyes throughout the day, you have probably noticed their pupils dilating at various points. Why are your cat’s eyes dilated? The team at Union Lake Veterinary Hospital is here to help you finally figure out this feline trait and better understand your cat.

Big Eyes for Big Excitement

Just like a little kid opening a present, your cat’s eyes will get big when he is feeling happy or excited. This can happen when he’s playing with his favorite toy, spying on a bird outside the window, or ready to pounce on some potential prey (or the laser pointer). If your kitty’s eyes dilate just before a fun activity, you can safely assume this is a physical manifestation of their excitement.

Fear in the Eyes
Pupil dilation could also be a sign that your cat is feeling scared about something. You might notice it happening when someone rings the doorbell. Or when a new animal comes over to visit, or you suddenly start playing a loud and unfamiliar noise inside your home. If your cat’s eyes are big because they’re nervous, try to speak in calm tones and give your cat some space to calm down.

The Eyes in the Lights

Your cat’s eyes might enlarge when the light changes in a room. If you’ve recently turned on a bright light or your cat has walked from a dark room to a lighter space, you might notice that his eyes change shape.

Cat’s Eyes Dilate When Something Is Wrong

If you notice any strange dilation with your cat’s eyes, it might be time to call your veterinarian. Unusual dilation could be a signal that something is going on with your kitty’s health. These pupil changes could be an indication of:

  • Excessive stress
  • A seizure condition
  • A bad reaction to medications
  • Ingestion of something toxic
  • Progressive Retinal Atrophy (PRA), which is a condition that could lead to blindness
  • Iris atrophy

Your veterinarian can examine your cat to determine if your cat’s eyes are dilated, the reason for the dilation and decide whether or not further treatment is necessary. If there is a medical issue at play, it is important to get quick medical attention. This is why it is so important to pay attention to your cat’s everyday behavior so you can notice when something changes.

Are your cat’s eyes dilated? We hope this explanation helps. Whether your cat is having a problem with his eyes or is ready for his next wellness exam, the caring team at Union Lake Veterinary Hospital is here to ensure your pets always get the veterinary care they need. To learn more about our services or to schedule your next exam, please call (248) 363–1508.

dilated pupil in cats one eye

My cat has had the same condition for 10 years by: Pixiegirl My male (also orange tabby)Boy has had a dilated pupil for about 10 years now. From what the vet was able to determine, he had probably had an accident or been hit by a car, etc. We do think he fell out of a tree. He was only sick/dehydrated for a few days, but as time went on, the dilation stayed. He needed surgery within 6 mos/year to pull back his …

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Why are my cat's eyes always dilated? - The Pet Care Tips

24-12-2021 · If the pupils of your cat’s eyes dilated for a short period and not constantly, then you don’t have to worry about anything. That may happen because of some basic reasons such as excitement, fear, or pain. However, the constant pupil dilation is a sign of Overstimulation, Stress, Anxiety, excessive pain, or even age-related atrophy.

24-12-2021

Seeing your cat doing unexpected things can freak you out, resulting in many questions. One of those questions is Why are my cat’s eyes always dilated? If your cat isn’t suffering from anything serious, then it might be adjusting its pupil according to the light. Apparently, cats also dilate their pupils to improve their vision. Other basic reasons for your cat’s dilated pupils are excitement, fear, or hurt. In such situations, pupils contract within an appropriate amount of time. But if your cat’s pupils are dilated long ago and aren’t contracted yet then, it’s concerning. We will thoroughly discuss several other reasons “why are my cat’s eyes always dilated?” Stay tuned and keep reading this article to know all about it.

Why do cats’ eyes dilate?

When you see your cat’s eyes dilated, you immediately start thinking what could be the reason behind it. If the pupils of your cat’s eyes dilated for a short period and not constantly, then you don’t have to worry about anything. That may happen because of some basic reasons such as excitement, fear, or pain. However, the constant pupil dilation is a sign of Overstimulation, Stress, Anxiety, excessive pain, or even age-related atrophy. You can prevent any of such severe health conditions by taking care of your cat’s eyes. Constant pupil dilation can cost your cat’s eyes, so be aware and do the needful. On the other hand, temporary dilation wouldn’t do much harm, but the veterinary doctor recommends getting checked once.

Constant pupil dilation of your cat’s eyes isn’t good news. It may indicate severe eye-related issues, and you shouldn’t take any chances and consult the vet as soon as possible. Eyes are a sensitive body part of your cat, and you need to take care of it quite sincerely. Any negligence can cost the eyes of your cat. Remember, temporary pupil dilation is normal, and there is nothing to worry about either. But if your cat’s eyes are constantly dilated, then you must get it checked by the vet. Further, we are about to discuss the reasons why your cat’s eyes are always dilated.

Reasons why your cat’s eyes always dilated

We understand, seeing your pet struggling with health issues isn’t very happening. As a matter of fact, your cat’s eyes should be in a normal state during the whole day. If not, it would be best if your cat gets diagnosed or treated sooner than later. You need to consult a veterinary doctor to avoid more damage to your cat’s eyes. Here are a couple of reasons they are causing constant eye dilation.

Poor Eyesight

Keeping eyes healthy needs constant care and protection, whether you, me or your pet animal. Poor Eyesight isn’t the only thing you should worry about here, as your cat might lose eyesight if the same situation continues for a long time. When we can’t see something at first glance, we rub them and adjust to the light and environment.

Well, the same goes with the cats as they try to adjust to the available light, and that’s why they dilate their pupils. Your cat is doing this too often to absorb as much light as possible to see things. It would be best to get your cat treated soon because it may permanently or temporarily lose its sight. Some blindness signs are as follows –

  • Easily scared by sudden noises.
  • Your cat finds it difficult to locate a water source.
  • Excessive distress or vocalization when you don’t respond.
  • Bumping suddenly into unfamiliar objects.
  • Apprehension when playing, jumping, and climbing.

If you absorb any of these signs in your cat, you need to help it. You can make your cat’s life slightly easier if it closes its eyes. Cats with poor Eyesight solely rely on their ability of hearing, smell, and touch. Please do the following things to help your cat when it loses its eyesight.

  • Keep the surroundings peaceful and less chaotic.
  • Please don’t move the things and furniture after your cat loses its eyesight.
  • Comfort your cat by interacting with it regularly.
  • You should keep necessary things in an obstacle-free path, such as food and water.
  • Let it know your presence by the stamp of your feet whenever you enter a room.

Stress and Anxiety

Stress and Anxiety can make your cat suffer mentally as well as physically. Apparently, these conditions can also cause the constant dilation of pupils. It is easy to tell if your pet is threatened or frightened by anything just by absorbing their behaviour. When you notice any of such signs, you need to help them overcome them. Generally, cats feel stressed or anxious because of loud noise or the presence of a stranger. If your cat continues to feel this way, it may become more aggressive in the future.

The only solution for dilating a cat’s pupils due to stress and anxiety is finding the cause. Once you find the cause driving your cat crazy, you can do something about it. You need to maintain a strict and reliable schedule to keep your cat calm, happy, and content.

Chronic Pain

Cats are predators by their nature, and showing pain doesn’t dwell with this personality. So, it would be difficult to identify if your cat is in pain at first. But if you know your cat well enough, it will be easy for you to recognise. No matter how hard the cat tries, it can’t hide all the symptoms of pain and suffering. The reason for the constantly dilated pupils of your cats can be chronic pain. If the dilations continue for an extended period, you should look for other symptoms. Those symptoms include aggression, irritation, loss of appetite, not interest in grooming, and even refusal for petting and handling.

Hypertension

Hypertension, also known as High Blood Pressure, can be a reason behind constant dilation of pupils. Blood pressure higher than usual can result in hypertension. However, older cats are safe from having high blood pressure, but the younger ones are at risk. The discomfort and pain during hypertension can lead your cat to dilated pupils.

If you notice any of such things happening with your cat, you should consult a veterinarian, as hypertension is often a secondary disease. There are high chances of being linked with other severe health concerns such as heart problems. If your cat is suffering from any other disease accompanied by hypertension, then you may see the following symptoms as well:

  • Irregular Heartbeat
  • Too much water consumption
  • Bleeding from the nose
  • Blood in the Urine
  • Circling

Medication Side effect

Cat’s pupil dilation can also be a side effect of their medication. Every medication affects every individual differently. So, there are chances that the certain medication has interfered or messed up the nerves that are indicating pupils to dilate or contract unexpectedly. Many different types of medication can interfere with the nerves and can make the pupils dilate. Some of them are Antihistamine, Stimulant Medications, Motion sickness patches, and Anticholinergic medications.

Dim Light

Working in dim light can affect anyone’s eyes badly. Neither you nor your pets should keep playing or working in low light. Dim lights can cause eye strain and headaches. So, it is better to work and play in an inadequate light. Please don’t put a lot of pressure on the eyes as it can make your cat’s eyesight poorer. However, keeping the lights off or low makes no difference while your cat is asleep. But if they are awake, don’t keep the light low or off. You can avoid any such painful situation by paying close attention to your cat’s eye health.

Iris Atrophy

Iris Atrophy is a progressive and rare eye disorder. Recognizing this eye disorder is slightly easier as it most frequently affects only one eye, developing slowly over time. If your cat is affected by Iris Atrophy, it will be unable to contract its pupils anymore. Unfortunately, Iris Atrophy is irreversible, but it will not cause too much pain. In this eye condition, Iris of the affected individual degenerates. This eye disease can affect cats of all ages and breeds, but it is commonly found in blue irises Cats.

Dysautonomia

Dysautonomia is also known as Key-Gaskell syndrome and can cause dilated pupils in the felines. It is a disorder of the autonomic nervous system, and a nervous system controls many reflexes and other involuntary neurologic functions. This disorder is susceptible for all breeds and age groups, but the younger cats are at much higher risk. Dysautonomia attacks a cat’s autonomic nervous system.

In simple words, a cat has no control over its basic functions. That’s why cats are unable to contract the pupils back after dilation. Dysautonomia needs to be treated as soon as possible, and constant eye dilation is a commonly recognisable symptom. There are some other concerns along with this condition, such as Dry nose, slow heart rate, low body temperature, Digestive issues, lack of appetite, and inability to urinate.

Poisoning and Toxicity

If your cat has consumed something poisonous or toxic, then its eyes would dilate. Such situations are life-threatening and need immediate action. If you come across any of such situations, you should bring your cat to the veterinary clinic. Other warning symptoms of toxicity are Trouble breathing, Vomiting and diarrhea, Low body temperature, loss of appetite, muscle tremors, and Lethargy. You can avoid any such situation by keeping the toxic items out from the reach of your kitty.

Overstimulation

Overstimulation refers to being too excited or interested in something. So, if you think that the reasons mentioned earlier aren’t your cat is suffering, then overstimulation can be your answer. Its pupils dilate when a cat gets excited due to sights, sounds, or even smell. Overstimulation is commonly found in cats and other pets when they find themselves in a new environment. Being too excited and exploring new surroundings results in dilated pupils—nothing to be stressed about as the pupils will contract when the cat calms down.

How to clean my cat’s eyes?

Cats are very enthusiastic groomers and spend a certain portion of their day grooming themselves. But they can’t reach some of their body parts and need your help. Assisting your cat while grooming will help both of you bond. While cleaning and brushing your cat, you need to be gentle as well. As mentioned earlier, cats’ eyes are also at risk and need to be taken care of accordingly.

For starters, you can clean the area around their eyes. If you can’t clean your cat’s eyes, then you can bring them to a grooming centre or veterinary clinic. Remember, cleaning is very important, or else your cat might catch some unwanted disease. Here are some tips for cleaning your cat’s eyes carefully –

  • Use lukewarm or warm water and cotton balls. Avoid using your fingertips. Use cotton balls instead.
  • Soak the cotton ball in the water and then gently wipe the gunk away from your cat’s eyes.
  • While cleaning your cat’s eyes, let it sit in your lap.
  • Make sure the water you’re using isn’t too hot.

Other than that, you can bring your cat to the vet if you aren’t sure you can do it, and experts know what to do better than anyone. So, take your cat to either the cat grooming clinic or veterinary clinic.

What does it mean when your cat’s pupils are big?

Dilated or big pupils aren’t always an indication of some disease or stress, but it may also suggest that your cat is excited. If your cat’s pupils dilate and contract soon, then it’s an indication of excitement and happiness. You must observe the period of the dilation because constant eye dilation isn’t healthy at all. It is a sign of disease. Earlier, we have discussed several reasons that many justify why your cat has dilated pupils. You must have noticed that pupil dilation also indicates that your cat suffers from other diseases. If so, then you should get it treated as soon as possible. A couple of things you should know about why your cat’s pupils dilate are as follows –

Medication

Going through medication or some other condition can also lead your cat to such a situation. Nor every medication would leave similar results on everyone. There are a couple of diseases whose medications can cause constant dilation of pupils in cats, including Antihistamines, Anticholinergic medications, and stimulation medications.

Light

Inappropriate light while staying up, working, or even playing can be harmful to your cat and for you as well. So, you shouldn’t keep the light dim at all. While your cat is awake, make sure it gets proper light to see things. Staying in low light for a long time can harm their eyes. Cat’s can sleep in low or even no light but keeping the light on while awake is necessary. Also, make sure that your cat is angry, stressed, or anxious about anything around them.

Injuries

Brain and eye injuries are also a big reason your cat’s eyes are dilated. You need to be more careful if your cat suffers from some severe disease. Regular veterinary visits would be helpful to keep a check on your cat’s health. A pet animal is dependent on you for most of their things, and leaving them in between isn’t a good idea. Rather than that, you should do everything possible to keep it safe, sound, and happy.

How to protect my cat’s eyes?

Regular cleaning can protect your cat’s eyes from any severe disease. You should not keep your kitty up in dim light as it puts pressure on their vision, and it would be best if you wash the eyes of your cat gently. Do not use soap to wash the eyes, and you can use only water to do so. As we have discussed earlier, cats’ eyes dilate when they are stressed, excited, anxious, and even in pain. If the dilation is temporary, then the pupils will contract soon enough, but if not, then you should consult the vet as it may be a sign of some serious health issue.

What are some common eye conditions your cat can have?

An unhygienic environment and an unclean body can result in many health-related concerns. Eyes are very sensitive and can get affected easily. So, you need to make sure that you are taking proper care of your cat’s eyes. If you see any of the symptoms that may result in a deadly disease, you should immediately consult a veterinary doctor. Some of the other eye conditions that your cat can have are as follows-

  • Cat Cataracts
  • Keratitis
  • Corneal Ulceration
  • Glaucoma

Final Words

That was all about why my cat’s eyes are always dilated and the reasons that cause this condition. I hope you found this article helpful. If any pet owner finds the symptoms early, they can help their kitty restore their vision. So, a regular health check from the vet is a great idea. We have mentioned all the required points in this article, but you can leave them in the comment section if you have any suggestive words. Your suggestions would help us to do better. Additionally, it would be nice to hear from our fellow readers.

Also Read:

  • Kinkalow Cats
  • How Much Space Does a Cat Need
vcahospitals.com

Anisocoria is a condition in which the pupils of the cat's eyes are different sizes; in other words, one pupil is larger than the other. In some cases, the abnormal pupil may be the one that is smaller and in other cases the abnormal pupil may be the one that is larger. What causes anisocoria?

In cats, the pupil is an elliptically-shaped opening in the middle of the iris that allows light to pass through the eye to the retina. The pupil constricts or dilates (enlarges) according to the amount of light that enters the eyes, with both pupils normally dilating in dim light and constricting in bright light.

What is anisocoria?404 image

Anisocoria is a condition in which the pupils of the cat's eyes are different sizes; in other words, one pupil is larger than the other. In some cases, the abnormal pupil may be the one that is smaller and in other cases the abnormal pupil may be the one that is larger.

What causes anisocoria?

Anisocoria is a sign of a disease of condition, therefore there can be several different causes, including:

  • Corneal injury such as an ulcer.
  • Disease or injury to the brain or to the nerves running to the affected eye, such as Horner’s syndrome.
  • Glaucoma, a disease in which there is increased pressure within the eye (the pupil in the affected eye will be dilated).
  • Uveitis, or inflammation of the interior of the eye (the pupil in the affected eye will usually be constricted).
  • Retinal disease.
  • Scar tissue formation between the iris and the lens (called posterior synechia), a condition that may develop following uveitis. 
  • Iris atrophy (a decrease in the amount of tissue within the iris) usually a degenerative change associated with aging.
  • Congenital defect of the iris, in which the iris tissue does not develop properly.
  • Cancer within the affected eye.
  • Spastic pupil syndrome - a syndrome that may be associated with feline leukemia virus infection.
  • Other infectious diseases such as feline immunodeficiency virus or toxoplasmosis.

If anisocoria occurs suddenly, you should consider this an emergency situation and seek veterinary care immediately to lessen the chance that your cat's vision will be permanently affected.

 

What else might I see with anisocoria?

In all cases of anisocoria, the pupil in one eye will be bigger or smaller than the one in the other eye. In some cases, that might be all that you notice. In other cases, depending on the underlying cause, the white part of the affected eye might be red, the cornea (the outer surface of the eye) might be cloudy or bluish in color, there might be a discharge from the eye, the eyelid on the affected eye might be droopy, the cat might be squinting or rubbing at its eye, or the cat may be less active than usual.

How is the cause of anisocoria diagnosed?

Your veterinarian will begin by conducting a physical examination of your cat, including a detailed examination of the structures of the eye. Depending on these preliminary findings, your veterinarian may do some further, more specific testing, such as measure the tear production and intraocular pressure (pressure within the eyes) for each eye. The cornea may be stained with fluorescein dye to look for underlying corneal injuries or ulcers, and conjunctival scrapings or biopsies may be obtained and sent to a diagnostic laboratory for specialized testing. Blood tests may be performed to determine if the condition is related to a systemic condition such as feline leukemia.

In some cases, your veterinarian may recommend a referral to a veterinary ophthalmologist for further diagnostic testing.

How is anisocoria treated?

The treatment of anisocoria depends entirely on the underlying cause of the condition, and specific treatment will be tailored specifically to the diagnosis. Your veterinarian will discuss the treatment options that are appropriate for your cat's individual circumstances.

Will my cat recover?

The prognosis for full recovery depends upon the cause of the anisocoria. In some cases, your cat may require long-term medication to control the underlying cause. If your cat became blind as a result of the underlying disease, it is extremely unlikely that the blindness will be reversible.

Why Are My Cat’s Eyes Always Dilated?

The reason cat’s eyes dilate when they play is because adrenaline is again pumping around their bodies. When hunting prey in the wild, cats need to be alert, fearless, and have lots of blood going to their muscles so that they can respond quickly and catch their …

Why Are My Cats Eyes Always Dilated

It is normal for pupils – the black part in the center of our eyes – to dilate and constrict to improve our vision.

At night when it’s dark they dilate to let more light in, and when it’s light they constrict and become smaller in size, allowing us to always have the optimal amount of light for the best vision possible.

Animals’ eyes work the same way, including cats’ eyes. But, what if your cat’s eyes are always dilated? Constant dilation is commonly a sign of hypertension, but could also be an indication that they are blind, are experiencing chronic pain, or have another underlying health condition.

However, if your cat’s pupils dilate periodically and as the light around them changes this is completely normal and not a cause for concern. It is only if you notice your cat has large pupils that are dilated all that time that you should be worried and get it checked out to ensure your cat’s eyes are in good health.

High blood pressure, also called hypertension, is the most common reason why your cat’s eyes are always dilated. Feline hypertension can be related to several factors, including kidney, thyroid, or heart disease, so be sure to take your cat to the vet so that they can prescribe effective treatment.

Although it is normal for cats’ eyes to become dilated when light conditions change, or to express fear, anxiety, or excitement, when cat’s eyes are constantly dilated it is a source of concern. They could be in a neutral state – that is neither overly constricted nor dilated – for the majority of the day.

Here are the most common explanations as to why cats’ eyes are always dilated.

Hypertension

As I already mentioned, the most common cause of dilated pupils in cats is hypertension. This means that your cat’s blood pressure is greater than 160mm Hg, which is more common in older cats or those that are overweight or obese.

It can be difficult for vets to diagnose hypertension, and abnormalities in cats’ vision is usually the giveaway sign, such as your cat having large pupils that do not constrict bright light. It is important you take your cat to the vets if you think they could have high blood pressure as if left untreated it can cause the retina to detach, resulting in blindness.

The treatment prescribed by your vet will vary depending on the cause of feline hypertension. It is often a secondary result of other underlying conditions, with the most common causes being kidney failure or hyperthyroidism. It is also possible that there could be no obvious cause, but this is extremely rare in cats.

Even once on medication to reduce their blood pressure, cats’ pupils can still remain dilated. This is because one of the drugs used to treat the condition can cause pupil dilation as a side effect. As long as you keep going to the vets to regularly check that their medication is still working, this is nothing to worry about.

Blindness or Loss of Vision

If your cat is losing their vision, their eyes may also be constantly be dilated. Just like how pupils dilate to aid our vision, cats that are struggling to see will have large pupils in an attempt to let as much light into their eyes as possible to aid their vision.

Aside from cats having round pupils, signs of blindness or poor vision also include bumping into objects and acting clumsy, being overly cautious when jumping or climbing, and acting more startled than normal.

If your old cat has dilated pupils, blindness could be the reason as cats’ vision does deteriorate with age. However, the problem could also be temporary and a result of kidney diseases, feline herpesvirus, or even severe eye infections.

Always take your cat to the vet if you suspect that they are blind. If it is only a temporary problem, your vet can prescribe the required treatment.

On the other hand, if your cat is permanently losing its site, don’t panic. Cats rely on their sense of smell, hearing, and touch a lot more than they do their vision. You may have to rearrange your living space to make it easier for your cat to navigate, but they will soon adust to having poor or no vision.

Anxiety Disorder

Another reason why some cats have round pupils is that they are scared, as when feeling anxious or worried, it is natural for a cat’s eyes to dilate. You may notice this if there is a sudden loud noise that startles your cat or the presence of an unknown person or animal.

However, if your cat’s eyes are constantly dilated because of fear, they may suffer from anxiety, meaning that they are constantly on edge. Sustained periods of high stress can trigger several other problems, including aggression or a loss of appetite.

If you notice that your cat is on edge and exhibiting other symptoms of stress, try to work out what the cause is. Has there been a change to their routine? Have there been new people or animals in your home? Are they having to compete for resources with other cats?

You can try to ease your cat into the new environment to help them feel more comfortable. Also, make sure you add plenty of places for your cat to hide in your home, such as a cat caddy or cardboard boxes. This provides somewhere for your cat to retreat to if they become stressed and need some time out.

Some cats are naturally nervous by nature. In these cases, medication may help to calm them down and relax. If the treatment is working, you will notice your cat’s pupils contract.

Chronic Pain

As cat’s pupils dilate when they are in pain, the reason why your cat’s pupils are so big constantly could be down to chronic pain. In fact, cats will instinctively try to hide that they are in pain because in the wild this will make them appear as a target to predators. Therefore, constantly dilated pupils are one of the only giveaways for cats who are in physical pain.

Alongside dilated eyes, your cat may also exhibit several other symptoms if chronic pain is the cause. Look and see if your cat has a loss of appetite, is being more aggressive or more tired than usual, or has lost interest in grooming.

To determine the source of your cat’s pain, it is best to take a trip to the vet. They will then be able to diagnose what is causing your cat continual discomfort.

With senior cats, a common problem is arthritis which can cause even more intense pain when moving. Usually, painkillers and massage therapy can help ease feline arthritis. Dental issues are another common issue, which are often accompanied by bad-smelling breath.

Feline Dysautonomia

Although extremely rare, it is possible that if your cat’s eyes don’t constrict they could suffer from feline dysautonomia, also referred to a Key-Gaskell Syndrome.

Feline Dysautobimia is a condition that affects your cat’s autonomic nervous system (ANS). This system is what controls all automatic bodily functions, such as heart rate, respiration, digestion, urination, arousal, blood pressure, and pupil dilation, among others. The ANS basically controls every essential bodily function that your cat needs to survive that does not need conscious thought.

For example, you don’t tell your heart to beat, it just does it. You don’t tell your stomach to break down your food, it just does it. You cannot tell your pupils to dilate or constrict, this just happens automatically. It is the same for your cat and for most other animals.

It is not known what causes this condition, but the most common early symptom is for your cat to have dilated pupils that do not respond to light. Dysfunction of the ANS can have several other effects, such as vomiting, an uncontrollable bladder and anal sphincter, difficulty breathing, loss of spinal reflexes, and muscle wasting.

It is important you take your cat to the vet immediately and document all the symptoms and when they started. As the cause is not known, only medication to treat the symptoms can be provided and most cats with this disease do no survive. For those that do, it can take up to a year to recover fully, and many will be left with some permanent dysfunction.

Remember that this condition is extremely rare, though worth highlighting. Also, an old cat with dilated pupils is unlikely to have Feline Dysautonomia as it typically affects young cats.

Anisocoria

Does your cat only have one eye that is constantly dilated? If so, your cat has anisocoria, which is where one of their pupils is a different size than the other. This is not a disease in itself, but rather a symptom of many other diseases.

Conditions that can lead to anisocoria include corneal ulcers, glaucoma, head trauma, and exposure to chemicals and toxins. Because of this, the treatment for anisocoria depends on the underlying disease that is causing it.

If your cat has glaucoma or a corneal ulcer, anisocoria may be accompanied by squinting or rapid blinking. Cats with glaucoma will also have bulging and bloodshot eyes too, along with behavioral traits due to the intense pain. On the other hand, if your cat’s anisocoria is due to toxicity, you will notice several other warning signs such as vomiting or diarrhea, tremors, muscle weakness, lethargy, and a reduced appetite. If trauma is the cause, the anisocoria will likely be temporary and not last longer than a few hours.

Regardless of what is causing anisocoria, a trip to the vet is a must if it lasts over 24 hours. The underlying cause will be identified and treatment will start to prevent further detrimental effects.

Feline Spastic Pupil Syndrome

If your cat has anisocoria that appears to alternate between eyes, this is called feline spastic pupil syndrome. This is a symptom of the Feline Leukemia Virus (FeLV).

Feline Leukemia is a serious condition and is the leading cause of death in cats after trauma. However, it is possible for cats to encounter the virus and fight it off, with 70% able to do this on their own. That being said, persistently infected felines will likely die within three years.

Because of this, if you notice your cat has feline spastic pupil syndrome then take them to the vet immediately. There is no cure for the disease, but regular check-ups and examinations can help prevent the infection from reoccurring and prevent complications.

Ocular Tumors

There is a possibility that cats whose eyes can’t constrict have tumors behind their eyes.

If your cat does have an ocular tumor, you may notice that as well as having dilated pupils because of the intense pain, they also suffer from inflammation, have cloudy eyes, or an iris which is misshapen. Glaucoma is also more common in cats with eye tumors.

These tumors may or may not be cancerous, but it is important to get the tumor removed as soon as possible and as a precautionary measure in case it spreads around their body. Small tumors can be removed by using a laser, but in the worst-case scenarios, your cat’s eye may need to be removed.

If this is the case, I would try not to worry. Cats adapt quickly and will have a perfectly happy life once they have become accustomed to having only one eye.

Iris Atrophy

Old cats with dilated pupils could suffer from iris atrophy as this is an age-related condition. As cats get older, the colored part surrounding their pupil known as the iris can thin.

Aside from giving your cat’s eyes their beautiful color, the iris is also a muscle that helps the pupil to contract in response to bright light. As this muscle thins, it gets weaker, making it harder to constrict the pupil which gives your cat’s eyes a permanently dilated look.

Thankfully, iris atrophy is not anything to worry about. Dilated pupils in cats cause no pain and rarely results in any long-term vision problems. The only change you may notice in your cat is that they become more sensitive to bright light.

Because pupil dilation can be a symptom of a much more serious condition, such as hypertension, glaucoma, toxicity, or blindness, it is still important to take your cat to the vet so that these other issues can be ruled out.

Medication Side Effects

Another reason why some cats have round pupils is a side effect of the medication they are on. Painkillers such as opioids are one of the most common types of drug that can cause pupil dilation in cats, such as buprenorphine.

You will likely know if this is the reason why your cat has dilated eyes because you will notice it occurring after each time you administer their medication. In addition, they may also suffer from other side effects of the medication such as excessive licking or pacing.

Usually, this is due to overdosage, so speak to your vet and see if you need to reduce the amount of medication you are giving your cat. You may also be able to switch to another pain killer that does not have the same side effects. That being said, dilated pupils are not a bad side effect and will not cause any harm.

Why Are My Cat’s Eyes Sometimes Dilated?

If your cat’s eyes are always dilated, a trip to the vet is needed.

However, it is normal for pupils to change size and react to different conditions. This is not a sign of concern and instead shows healthy eye function, allowing your cat to have better vision in different light conditions, as well as a natural response when excited or scared.

Better Vision

You will notice that your cat’s pupils dilate and constrict in response to changes in light levels. In bright light, they will constrict to protect the back of the eye, but in the dark, they will dilate to let as much light in as possible.

If you are wondering can cats see in the dark, their vision is not perfect and they cannot see any more than we can in the pitch black. However, they can see much better in low light conditions, which is all thanks to their pupils dilating and letting as much light into their eyes as possible.

Because of how your cat’s pupils respond to light, your vet will often use a bright light to test their eye function. If they shine a bright torch into your cat’s dilated eye and it does not constrict, they know there is an underlying problem.

Surprise or Fear

Cat’s eyes will also dilate when they are surprised or scared.

When your cat is scared, they produce large amounts of the hormone adrenaline to give them the best chance of survival. This adrenaline makes them feel more fearless, but it also has changes on their body, such as increasing their heart rate and sending more blood to their muscles, heart, and lungs, priming them to run away from a bad situation or get ready to fight.

Another side effect of adrenaline is that it makes cats’ pupils dilate. So, if your cat’s pupils are big and round, it is best to leave your cat be. It could be anything from a loud noise to an unknown house visitor that makes your cat feel scared, so leave them time to settle and realize they are still in a safe space and approach them when their eyes are back to normal.

Excitement

If cats’ eyes dilate when they are scared, then why do cats’ eyes dilate when they play? Are they scared of their toys? Are they not enjoying playing with you?

This often confuses owners, but having dilated pupils can also be a sign of excitement. This seems confusing as two very opposite emotions trigger the same response in their eyes. However, you can easily tell the difference between the two by observing the environment.

If you are playing with your cat or have just given them a treat, then it is safe to assume that their pupils are wide and dilated because they are excited. However, if they are hiding under your couch during a thunderstorm, they are likely scared.

The reason cat’s eyes dilate when they play is because adrenaline is again pumping around their bodies. When hunting prey in the wild, cats need to be alert, fearless, and have lots of blood going to their muscles so that they can respond quickly and catch their next meal, and they rely on adrenaline for this.

For cats, their version of playing is hunting – playing with toy mice, chasing bits of string, or pouncing on their cat kicker toy. Therefore, adrenaline will be pumping around their bodies as they play, making their pupils involuntarily dilate.

CONCLUSION

Although having pupils that dilate and constrict in different circumstances is a sign of good feline health, if your cat’s eyes are always dilated it can be concerning. Cats’ eyes often give away a lot about how your cat is feeling and can be the first obvious symptom for many underlying conditions.

If you notice your cat has permanently large pupils, take them to the vet as soon as possible. Usually, hypertension is what is causing their pupils to dilate, which is a secondary condition for several illnesses. Therefore, it is important your vet can diagnose the underlying problem and provide effective treatment. Other conditions could also be the culprit, and the majority can be managed with the correct treatment.

The most important thing to remember is not to panic. Follow the advice of your vet and your cat will likely be well and back to normal in no time at all.

animalsjournal.com

Constant dilation of cats' eyes can be a sign of pain, overstimulation, or age-related atrophy. Various health concerns are connected to dilated pupils, including feline leukemia, toxicity, dysautonomia, and tumors. Cats' eyes should dilate periodically, so it's a real concern if the pupils never contract.

  • Asked by: Dr. Rhiannon Cormier

    Last update: October 24, 2021
    Score: 4.2/5 (55 votes)

Constant dilation is commonly a sign of hypertension, but could also be an indication that they are blind, are experiencing chronic pain, or have another underlying health condition. ... High blood pressure, also called hypertension, is the most common reason why your cat's eyes are always dilated.

An excited or playful cat may have wide dilated pupils as they get ready to play. However, fear or surprise could also lead to the same result. Changes that occur due to excitement or fear should be relatively short lived. As the cat relaxes the obviously large pupil should return to a smaller size.

Constant dilation of cats' eyes can be a sign of pain, overstimulation, or age-related atrophy. Various health concerns are connected to dilated pupils, including feline leukemia, toxicity, dysautonomia, and tumors. Cats' eyes should dilate periodically, so it's a real concern if the pupils never contract.

Pain also can be indicated either by a constricting or dilating of your cat's pupils. Pain in the eyes themselves is usually accompanied by the constricting of a cat's pupils, while pain elsewhere in the body can be accompanied by dilated pupils.

A cat's pupils can shrink to the narrowest of slits or widen into black pools. Eyelids may be fully open, partially closed, or drawn into a squint. Causes for these changes may be emotional arousal, such as fear, aggression, pleasure, or excitement, or environmental, such as a change in ambient light levels.

43 related questions found

You can generally characterize signs in 3 categories: go, stop and yield. The cat's pupils are generally vertically compressed as in the picture above. Sometimes, they will look round. This means that they are dilated.

Their eyes are intelligently designed

According to Catster , the reason cats' night vision is so excellent is because of the intelligent design of their eyes. They possess a curved cornea and large lens, and in low light their pupils can dilate to full circles to allow in maximum light.

One of the signs that may be noticed though is that the pupils (the dark central part of the eye) usually become very dilated if a cat becomes blind.

Signs that your cat is in pain include:

  1. Agitation (unsettled, trembling)
  2. Cat crying, growling, hissing.
  3. Limping or difficulty jumping.
  4. Avoids being petted or handled.
  5. Playing less.
  6. Licking a particular body region.
  7. More aggressive.
  8. Change in posture or gait.

A wide variety of conditions can precipitate sudden blindness in a cat, including a burst of bleeding into the eye's interior or a traumatic blow to the head. In rare cases, a cat's ingestion of an antibacterial medication called enrofloxacin has also been shown to damage the feline retina and cause sudden blindness.

How to tell if a cat is blind

  • Cloudy eyes.
  • Uneven or very wide pupils.
  • Disorientation and bumping into things, especially in low light.
  • Walking slowly/cautiously with their legs wider apart than usual. ...
  • Reluctance to jump.
  • Hiding away and becoming nervous.
  • Reluctance to go out at night.
  • Changes in their behaviour.

If the cat eyes are narrow and the eyes are squinted, that's a sign of aggression. The squint helps to protect her eyes from an opponent's claws. However, if the cat pupils are narrow and your cat is relaxing on your lap and purring, you can probably guess that she's experiencing great pleasure.

She'll probably be in pain and may snap or growl if you touch her hind quarters, so you'll need to be extraordinarily gentle. Vertebrae dislocations can often heal on their own, but if a severe breakage occurs, your veterinarian might have to amputate her tail.

Relief and Healing

Even though purring takes energy, many cats purr when they get hurt or are in pain.

A blind cat can have a wonderful, happy life. ... It is not cruel to allow your pet to function as a blind pet. In fact, blind pets are not nearly as concerned about their deficit as most owners. When your pet becomes blind, the cat will just rely on its sense of smell and hearing.

Consider crate training your blind pet if they'll be left alone for long periods of time or confine them to a small space when you leave. Provide noise-making toys that they'll be able to easily find or give them treat-dispensing toys that they can find by smell.

Strokes in cats occur when blood flow to the brain suddenly gets interrupted, often due to a blood clot. Signs of a stroke in cats include stumbling, pressing their head against a hard surface, and weakness.

Cats have learnt to miaow for the same reason, as they have no need to communicate in this way with other cats. ... As well as being a method of communication, staring is also a sign of a close bond between you and your cat, as they are unlikely to hold eye contact with someone they don't like or trust.

When a cat trusts a person they usually do not feel to be on alert so that when she closes her eyes when being petted it is an ultimate sign of trust. ... Aside from being appreciative, enjoying the gestures and as an expression of trust, your cat may also close her eyes because she feels extremely relaxed.

Cat owners are often encouraged to slowly blink or wink their eyes (e.g. sleepy eyes) when directly looking toward their cats. This sends a message that you are not a threat and they should not be alarmed. However, cats always prefer their owners using their peripheral vision to look at them rather than a direct gaze.

Iris melanosis is darkening of the iris of cats that occurs from proliferation of cells that produce a brown pigment called mela- nin. ... The condition may occur in cats with any color of eye and at any age. In many cats, the progression of the melanosis is very slow (several years).

Cats slap us with their tails for all types of reasons. It's a cute behavior, and it's more of a gentle tap than a slap. From feelings of frustration to excitement and curiosity, your cat uses tail slapping as a communication tool to get your attention and let you know how it's feeling.

Pulling on a cat's tail could actually paralyze your cat. Oftentimes, when a cat's tail is damaged, it results in rear paralysis in the body. ... If your cat does get its tail hurt, take a visit to a local veterinary hospital for help.

Do cats feel love? It's a question that many cat owners have wondered. And the answer is a resounding yes! Cats often feel love quite strongly for their owners and other companions.