Unequal Pupil Size Average Cost

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Average Cost

$1,000

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What is Unequal Pupil Size?

Normally, the pupils expand and contract in unison. When unequal pupils occur, the abnormal eye can be either the smaller (constricted) pupil or the larger (dilated) pupil. There may or may not be other symptoms present. If unequal pupils occur suddenly, bring your cat to a veterinary clinic or animal hospital immediately as eyesight can be permanently damaged if the problem is not rectified. Certain underlying causes of unequal pupils can be life threatening.

Unequal pupils, or anisocoria as it is called in the medical community, occurs when one of a cat’s pupils (the black openings in the center of the iris) is either too far open or too far closed in relation to the other pupil. This gives the appearance of a small black dot in the center of one eye and a larger black dot in the center of the other. This condition is often the result of a more serious complication within the cat.

Symptoms of Unequal Pupil Size in Cats

Only one symptom need be present to merit a veterinary examination. If any of the following arise after head trauma, veterinary attention will be needed immediately. 

  • One pupil larger than the other
  • Eye producing discharge
  • Drooping eyelid
  • Redness of the eye
  • Clouding cornea
  • Bluish cornea
  • Head tilting
  • Eye pain or irritation
  • Squinting
  • Activity decrease
  • Abnormal eye movement
  • Confusion
  • Change of position of eye in socket

Causes of Unequal Pupil Size in Cats

Unequal pupils can be caused by both neurological (brain or nerves) and ocular (eye) issues. Because the eyes are so closely connected to the brain, often damage and injury of this area affect both parts of the body. All known causes include:

  • Concussion (bleeding and swelling of the brain from head trauma)
  • Injury to optic nerves
  • Neurological disorder (such as Horner’s Syndrome)
  • Oculomotor nerve paralysis (damage to the nerve controlling eye movement)
  • Cerebellum (brain) injury
  • High blood pressure
  • Corneal ulcer or injury
  • Glaucoma (pressure from excess fluid dilates the pupil)
  • Anterior uveitis (inflammation of urea constricts the pupil)
  • Retinal disease
  • Scar tissue
  • Iris atrophy (mainly in older cats)
  • Defective iris from birth
  • Cancer or cancerous tumors
  • Spastic pupil syndrome 
  • Feline leukemia virus
  • Stroke (ruptured blood vessels in the brain)
  • Eye infection
  • Medication (some can cause the pupils to dilate)

Diagnosis of Unequal Pupil Size in Cats

To start the diagnostic process, the vet will require your cat's full medical history along with all current prescriptions ,including eye drops. Next, the vet will complete a physical examination with detailed focus on the eye region. You will be asked if your cat has undergone any recent trauma that you are aware of. The main objective will be to determine if the unequal pupils stem from a neurological problem or an eye problem. 

Many tests may be administered at this point. Often, the function of the pupils will be evaluated using Visual Pathway Testing. This includes checking for blinking reflexes, object following ability, and proper light sensitivity. Tear production may be measured with a Schirmer Test. Topometry may be applied to test for intraocular pressure. The cornea may be stained with dye to better find ulcers, scratches or other injuries. An ERG (electroretinography) test may be conducted to measure the function of cones and rods within the eye. 

Biopsies or conjunctival scrapings may be collected and sent to labs for further analysis. Blood tests and complete blood counts may be needed in cases which Feline Leukemia Virus or cancer are suspected. An ultrasound, MRI or CT scan may be requested if tumors or lesions are present. Spinal fluids may need to be collected and analyzed in some cases of neurological issues. Urinalysis may be needed in cases of infection. Obvious signs of disease will be noted for diagnostic purposes. If no cause is found, the cat may be referred to an ophthalmologist for further inspection.

Treatment of Unequal Pupil Size in Cats

As unequal pupils are often the sign of an underlying issue, treatment depends on the issue and not the condition of the pupils themselves. Severity of underlying issues range from harmless to life-threatening. Common issues and their recommended treatments are listed below.

Medication 

In some cases, a medication will be found to cause unequal pupils. If this is the situation, the removal of the medication should stop the pupil issue. 

Glaucoma 

Often medication will be prescribed for this condition, fixing the unequal pupils in the process.

Infection 

If eye infections are found, the responsible bacteria will be identified and the appropriate antibiotics will be prescribed. The average time needed for antibiotics is 2-4 weeks.

Cancer 

If tumors are found, surgery may be an option. The cat would be put under general anesthesia for the procedure. Recovery time will depend on the location of the tumors. Radiation or chemotherapy may also be treatment options to fight against cancer. Both have strong side effects and treatment can be lengthy.

High Blood Pressure 

This can be alleviated with ACE (Angiotensin Converting Enzyme) inhibitors, beta-blockers, calcium channel blockers and a low sodium diet. This treatment may be ongoing. 

Horner’s Syndrome 

This issue will generally resolve on its own, but eye drops may be prescribed to help with symptoms. 

Feline Leukemia Virus 

No cure is currently known, so care designed to ensure the cat’s comfort would be advised.

Hypoplasia & Iris Atrophy 

Both of these conditions require no treatment. 

Recovery of Unequal Pupil Size in Cats

Depending on the underlying cause of the unequal pupils, recovery can be possible. Often medications will be prescribed over a long period of time. If vision loss or blindness have occurred in the cat, they are often not reversible.

If Feline Leukemia Virus is found to be the cause, focus on all at home adjustments you can make to lengthen your cat's life span. This would include keeping the cat indoors, removing all sources of stress, changing the cat's vaccination schedule, following all antibiotic prescriptions for related infections closely and giving your cat vitamins and anti-viral drugs.

No matter what the underlying cause of unequal pupils is, if the condition does not improve, or if it gets worse, more veterinary care may be needed. 

Unequal Pupil Size Questions and Advice from Veterinary Professionals

Smokey
Mix
14 Years
Mild condition
0 found helpful
Mild condition

Has Symptoms

Uneven Pupils

My 14 year old cat has uneven pupils. I took her to the vet and was prescribed drops for her. She went back to the vet for a re-check and she only got 30% better. He gave her a steroid shot and I am to continue the drops for another 2 weeks. She is not acting any different just the 2 different pupil sizes. Should I go for further testing or see if she has any more changes in behavior?
Thank you

Dr. Michele King, DVM
Dr. Michele King, DVM
876 Recommendations
Ideally, Smokey would be able to get an MRI to determine what the cause of the different sized pupils might be. Barring that test, it would be best to trust your veterinarian, as we often use response to therapy or changes in behavior to help guide therapy for different situations. I hope that she is okay.

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Nala
domestic short hair
10 Months
Mild condition
0 found helpful
Mild condition

My 10 month old kitten yesterday would not open her eye and was not playing she slept most of the day . When I opened her eye to see what was wrong her pupil was very very small I didn’t see any discharge coming from the eye but I sent my husband to go pick up nutri vet eye rinse ! Today she is very active and eating and her eye is open but her pupil is very dilated I was wondering if it was from the eye rinse since it has boric acid in it or if I should take her to the vet

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
A dilated pupil and closed eye may be due to a traumatic injury (including head trauma), poisoning among other conditions; you should keep an eye on Nala for the time being but if any other symptoms present or there is no improvement in the dilated pupil you should visit your Veterinarian tomorrow for an examination. Regards Dr Callum Turner DVM

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Morty
mixed
6 Months
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Eye Clouding
Pupil not contracting
Lack of energy

My cat was fine this morning when I went to work and I just got home now and he is different. He is not running around or playing. His right eye is squinted shut and when I do see his eye it is a different shade, a tiny bit cloudy, and his pupil isn’t reacting like the other one. I am scared and don’t know what to do

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
There are a few possible causes, but generally a traumatic injury to the eye would cause these symptoms (i.e. by walking or running into something); you should try to flush the eye with sterile saline and see if there is any improvement. If the pupil still doesn’t react to light, you should visit your Veterinarian for a thorough examination and a check of intraocular pressure. Regards Dr Callum Turner DVM

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MrKitty
Shorthair
9 Years
Moderate condition
0 found helpful
Moderate condition

My cat got some tubes of medicine put in his ears to treat ear infections. About 3 days later, one of his 3rd eyelids started showing and the pupil isn’t dilating like the other. The vet didn’t seem super concerned after looking at his eye closely and gave us antibiotic drops. They said we should see improvement in 24hrs. It may be marginally better but it’s been 3 days almost. I’m not confident treating it as an infection was the answer. Any suggestions? I don’t want to be that spastic pet owner who runs to the vet for no reason, but I don’t want MrKitty to suffer needlessly either.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
Sometimes infections or other conditions affecting the ear may affect the eyes due to nerves running through the middle ear which may lead to Horner’s Syndrome and similar symptoms. If your Veterinarian isn’t concerned, complete the course of treatment and return if there is no improvement or symptoms get worse; without examining MrKitty I cannot say whether the correct treatment was given. Regards Dr Callum Turner DVM

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Tori
Tiger cat
8 Years
Fair condition
0 found helpful
Fair condition

Has Symptoms

Uneven Pupils

I took my cat to the vet about a week ago for her uneven pupil sizes and the vet said that her eyes reacted normally to light and that everything is fine, and sometimes this happens with cats as they get older. I've been doing some research and no site has said that uneven pupils were a symptom in older cats. should i bring my ball of sunshine to another vet to double check her eyes or is this information right?

Dr. Michele King, DVM
Dr. Michele King, DVM
876 Recommendations
Thank you for your email. Uneven pupil sizes are not normal, no. It may be an indication of trauma, brain disease, or nerve dysfunction. It may not be a condition that needs to be treated, but it isn't normal with aging. It might be worth a second opinion to make sure that Tori is okay.

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Grayson
Persian
6 Months
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Uneven Pupils

My Persian cat was shut in the dryer for approx 6min with bedding/ pillows. When I checked the dryer, due to sound, he was distressed of course and panting. Upon further examination I noticed that one pupil is not dialating the same. He is exhausted, as understandable but steady on his feet, cooled down well, and respiratory rate seems good, as he is sleeping now. He jumped off of the bed without a problem and was grooming himself before going to sleep. I have a home visit already scheduled tomorrow for all three of my cats at 2:00pm and wonder if waiting for that visit would be okay to assure his well being?

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
Personally, I would take the cautious approach and have Greyson seen immediately especially since it seems he was inside the dryer whilst it was on? If this is the case there may be various different issues with his health including head injury which should be seen as soon as possible. Regards Dr Callum Turner DVM

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Molly
Mix
12 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Bad vision

My cat’s iris is overlapping her pupil, but it looks almost like it’s torn or something. She has bad vision but her eyes looked normal aside from her pupils being very large until this happened. It’s only on the right eye; the left eye looks as it usually does. She is a very old cat, but we don’t know the exact age since she was a stray.

Dr. Michele King, DVM
Dr. Michele King, DVM
876 Recommendations
Thank you for your email. Without seeing Molly's eye, I'm not sure what might be going on with her, or if any treatment is needed. It would be best to have her seen by a veterinarian, as they will be able to examine her, assess her eyes and determine what is happening, and recommend any testing or treatments that might help. I hope that everything goes well for her.

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Triomino
Domestic shorthair
12 Years
Mild condition
0 found helpful
Mild condition

Has Symptoms

Eye Redness

Hello,
Yesterday morning we noticed my cat had more waxy dark build-up in the right ear. We mixed a solution of 1 part water, vinegar and alcohol, like our old vet had told us when the cat was younger, to clean the ear. Directly after putting the solution in the ear and wiping woth cotton balls, the cats second ear lid came up and the pupil on the right side shrank. The left pupil dilated. We thought maybe some solution got in the eye as he was squinting as if it had. The cat’s eye watered and remained like this for an hour. The cat was shaking his head and keep his ear lowered as if it was irritated and not all solution was not out yet, but was not scratching or pawing at the ear. We thought maybe some solution got in the eye. We watched the cat for several hours n the second eye lid mostly receded, but the pupils remained unchanged and he was still squinting as if his it got in his eye. It has been several hours, the cat is no longer shaking the head and ear seems fine. However, the cat is still squinting the right eye with the second eye lid showing and the pupil smaller amd the left eye open with a larger dilated pupil. Coupd the silution have injured the cats eye?

Dr. Michele King, DVM
Dr. Michele King, DVM
876 Recommendations
Thank you for your email. A couple of things are possible. A small amount of the solution may have gotten in Triomino's eye and caused irritation, or he may have a ruptured ear drum and the solution irritated the nerves inside his middle ear. WIthout examining him, I can't see his eye or ear, so am not sure what might be going on, and it would be best to have him seen by a veterinarian, as they can look into his ear canal, assess his eyes, and prescribe any medication that might be necessary for either. I hope that he recovers well!

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Little Male
Bengal
1 Year
Critical condition
0 found helpful
Critical condition

Has Symptoms

limp
Crying
Hard time breathing
bluish ears
impaired mentail status
Uneven Pupils
Shaking

Hello, today I walked outside to leave the house and my cat was laying on the ground crying in pain, I put him in a box, next to a heater. His mental status is very poor. He is unresponsive and limp. I am afraid he is dying however, I am not able to take him to the vet. His breathing is very poor and he stretches his neck to try and breath. His eyes are unequal in dilation. He makes whimpers. His ears are sort of blue, and is currently lying on his side barely breathing. His gums are sort of whitish. Yesterday he was acting fine, and today he is dying. Also, a little background information is that he is an outside cat and I think a little over a year old and has some bengal in him. I just want to know what is wrong with him. I feel like he may die in the next 24 hours or so. Thank you very much!!

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
Your cat requires veterinary attention immediately, I cannot say for sure what the specific cause of the symptoms are but blueish ears, white gums and difficulty breathing are indicative of anaemia/hypoxia; the unequal pupils, shaking and lack of response may be secondary to trauma, poisoning or another cause. You should visit a charity clinic or try to get help with the cost of Veterinary care, check the link below. Regards Dr Callum Turner DVM www.aaha.org/pet_owner/lifestyle/cant-afford-critical-veterinary-care-many-nonprofits-can-help!.aspx

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Nessa
American Shorthair
1 Year
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

R. Pupillary Resp Decr (small size)
No confusion
Responsive and alert
Discomfort (eased with cold pack)
R. Eyes swelling
Squinting
Less active
Discharge

Medication Used

none

I came home from work today and my youngest kitten Nessa seemed off. She greeted me like normal but has played less and shown the listed symptoms. (Smaller right pupil, swelling of that eye, squinting and discharge) She hasn’t seemed confused or anything other than lethargic. I did a cold compress on the eye for 15 minutes every hour since I came home and that seems to have eased her discomfort a great deal (she’s sleeping instead of pawing the eye and has even cleaned herself since). Obviously I’m still concerned and am on a limited budget as far as my options go. How concerned should I be and do I have any options other than direct veterinary testing?

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
There are various causes for unequal pupil size which may be localised to the eye (infection, uveitis, trauma, glaucoma among others) or may be due to other factors (head trauma, poisoning, neurological disorders etc…). You should have Nessa examined by a Veterinarian because I cannot determine the cause or severity without examining her, I understand finances may be tight but there are charity clinics and other organisations which may be able to help. Regards Dr Callum Turner DVM

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Boo
Mixed (Maine coon and alley-cat)
2 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

single constricted eye
Swollen area around eye
Unequal pupil size

I have a 2 year old cat named Boo, and he is half Maine coon, half alley-cat. Is it okay for him to have unequal pupil sizes? We moved recently so I think it may just be dust or some kind of allergies, but all of sudden his left eye is constricted/ less dilated (both of his eyes are usually very dilated also), and his left eye seems more squinted, and the area around it seems almost swollen. I saw him itch around it maybe once but that was probably nothing. Everything else seems normal and he also doesn't seem in any pain and isn't any more sensitive when we touch/pet him around there. Just wondering if I should worry or not. Thanks!

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
Any changes or differences like unequal pupil size should be seen by your Veterinarian as there are multiple conditions which may be affecting Boo which may include head trauma, neurological disorders, glaucoma, poisoning, eye injuries among other causes. Without examining Boo and checking intraocular pressure I cannot say for sure. Regards Dr Callum Turner DVM

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blue
Scottish Fold
2 Months
Fair condition
0 found helpful
Fair condition

Has Symptoms

discharge under eyes
unequal pupil sizes

Is it normal for my kitten to have unequal pupil sizes, could that lead to any serious conditions? she has a lot of discharge under her eyes, and one of her pupils is larger than the other. sometimes her eyes tilt in different directions, she's only two month old, and i've only started to notice this recently

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations

There are many different causes for unequal pupil size, some are quite serious: infections, head trauma etc… It would be best to bring this up with your Veterinarian during a vaccination visit as Blue should be getting regular shots at her age.  Regards Dr Callum Turner DVM

Very helpful

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Panda
Persian mix
13 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

dull fur
Pupil dilated
Watery eye
Lethargy
Loss of Appetite

Medication Used

Buprenorphine
Neomycin
Clindamycin Hydrochloride
NeoPoly Dex Drops

We took our 13 year old cat into the vet as she just didn't seem herself for a couple of weeks. She seemed thinner and her coat was less glossy. She was still eating, but not as much, and one of her eyes was watery. The vet sampled her blood and found no immediate cause for concern, gave her a check up where everything seemed relatively normal (no fever, no pus). He gave her a shot of antibiotics and some to take home as well as pain relief and eye drops. Since being on medication she's hardly eaten or gone to the bathroom at all, her inner eyelid now shows on the affected eye and her pupil is large constantly in that same eye. I discontinued all meds for the day and she seems to perk up - but something still isn't right. Any thoughts? Could it be something in her mouth or head? She doesn't want to move from her favorite sleeping spot.

Dr. Michele King, DVM
Dr. Michele King, DVM
876 Recommendations
Thank you for contacting us about Panda - I'm sorry that she is having these problems. While it is uncommon, cats do have reactions to medications. Whether she is having a reaction to the eye drops or whether her signs are a progression of something that is going on with her would be worth pursuing with a recheck at your veterinarian. They will be able to examine her and make sure that she is still basically okay, or if she needs different treatment . I hope that she is okay.

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Echo
Russian Blue
2 Years
Serious condition
1 found helpful
Serious condition

Has Symptoms

Cloudy eye
Redness
Squinting
Dialated

My cat Echo who is 2 and a half years old is having issues with her left eye. Her left eye is very cloudy and dialated differntly than her other eye, sometimes its bigger and other times its smaller. She also has redness in the eye and she squints most of the time. Other than the squinting I don't notice her in very much pain. She eats and drinks water like normal but i dont notice her using the litterbox as much anyone. Im very worried about my cat and would love to have an opinion on what I should do and what it could be. Thank you in advance.

Dr. Michele King, DVM
Dr. Michele King, DVM
876 Recommendations
Mary, thank you for contacting us about Echo. Without examining her, I can't diagnose anything, but it sounds from your description like she may have an infection or inflammation in her left eye. It may be a superficial infection that needs antibiotics, but sometimes cloudiness can occur in the eyes due to an underlying disease, and she may need some blood work or testing for infectious diseases like Feline Leukemia. It would be best to take her to your veterinarian and have her checked out - they will be able to examine her eye and let you know more about whether it is an infection, inflammation, or otherwise, and what can be done to help her heal normally. I hope that everything goes well with Echo.

Thank you. From the decription does it sound like it could be pink eye because I am currently giving her some eye drops for pink eye?

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Toby
Stray orange Tabby
2 Months
Fair condition
0 found helpful
Fair condition

Has Symptoms

One pupil smaller than the other

Hello I'm recently nursing an abandoned kitten. When we found him he was cold and very under weight. He's doing much better and is very active but one of his pupils will be smaller than the other sometimes. Its not constantly smaller, it comes and goes and last maybe 20min tops. He only has this one symptom and is other wise very playful and aware of his surroundings. What do you suggest?

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
For the time being keep an eye on Toby, but soon you should start thinking about vaccinating him (regardless of whether or not he will be an indoor cat or not) and at that time bring his eyes to the Veterinarian’s attention. Unequal pupil size may be caused by a variety of different causes and your Veterinarian will be able to advise you on whether any treatment is necessary. Regards Dr Callum Turner DVM

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Levin
Domestict short hair
unknown
Mild condition
1 found helpful
Mild condition

Hello. My cat was given a sedative to get shaved as he had mats all over his body and would not let anyone touch him. While my cat was under he also got 3 vaccinations. This was on 10/21/2017. After he got home he could barley walk from the medication and his eyes were moving from side to side rapidly. I placed him in my room with food, water, and a litter box and watched over him for the next 48 hrs. At the 48 hr mark my cat had still not ate or drank anything. One of his pupil was dilated and blurry and the other one wasn't. He was still unable to walk with out falling over so I took him to the ER. He was put on fluids for 48 hrs and came back home to me. The doctors could not diagnose him as this was the first time they encountered a cat with these issues from sedation. it is now 11/04/2017 and my cat is eating only wet food which is not usual for him. He is drinking lots of water and frequently peeing. He is also walking on his own finally without falling over however still has one pupil dilated. The dilated pupil is not blurry so that is good but my cat is also still a little unaware of his surrounds and just kind of off. Can you help? I am not sure if this is something neurological or just something temporary.

Dr. Callum Turner, DVM
Dr. Callum Turner, DVM
2318 Recommendations
It has been two weeks since Levin was sedated, any short term effects should have resolved by now; I am trying to think of any side effects which may be related to the sedation or vaccination. It is possible that the unequal pupil size is related to inflammation due to vaccination but I cannot see why the issue is continuing after two weeks. I am unable to shed any further light on this. Regards Dr Callum Turner DVM

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