Categories: eye disease

My Cat has Dilated Pupils

I have a beautiful long haired tabby/ tortoiseshell cross 1 year old but her right eye pupil is wide open and does not dilate, the left eye is similar but not as bad, the vet finds this ‘strange’ but is obviously not familiar with the problem. Can anyone help please?


Hi Derek: I am not sure that you have described the problem accurately. If the pupil is wide open it is dilated it seems to me. Perhaps you mean that it does not change shape or narrow. The pupil is the opening in the center of the eye through which the light passes and which is narrowed or enlarged to control the amount of light entering the eye. The iris (a muscular structure) opens and closes the pupil. In the cat the pupil is slit like and the amount of light entering the eye can be further controlled by the eye half closing and going over the slit.

If the iris is not responding to different light levels by closing and opening the pupil that would indicate to me that your cat is blind i.e. light is not being received and no signal is being sent to the brain to regulate its impact on the retina. Blind or partially sighted cats can cope very well and therefore hide the problem.

Sudden blindness is often caused by Untreated Feline Hypertension. Early signs to watch for include dilated pupils which don’t respond to light. This is what is happening with your cat it seems to me. A low-sodium diet may be the answer but your vet can advise.

But this is perhaps a simplistic answer. Your vet should be fully aware of this. There is no substitute for a good vet providing advice on the spot.

From My cat has dilated pupils to cat health problems.

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My Cat has Dilated Pupils

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Dec 02, 2011 Review of comments
by: Michael

This page has been here for some time and I have reviewed the comments. It seems that in all cases a dilated pupil has indicated blindness or partial blindness. This does not surprise me as the closing of the pupil is a response to seeing bright light. If the cat can’t detect this it won’t close.

Cats compensate well which masks problems. Conditions that affect eyesight are:

Retinal diseases

Progressive Retinal Atrophy – retinal cells degenerate. No treatment.

Retinitis – inflammation of the retina. Cells become damaged. This disease occurs in association with toxoplasmosis, FIP, lymphoma, cryptococcis, systemic fungus infections, hypertension (high blood pressure is a common cause), eye injury, Retina may become detached

Central Retinal Degeneration

Dietary problem can be the cause – lack of taurine in diet. Causes partial blindness.

Another cause – antibiotic enrofloxacin.

Hope this helps.


Dec 01, 2011 dilated pupils
by: betsey

i have had 2 older cats in the last 6 months with this problem-almost overnight the first one had horrid red streaking in eyes-rushed to vet-blindness occurred due to very high blood pressure that blew out his retinas-some vets do not have equipment to test for bp-he has adjusted well with meds and gets around well-second one has it too-seems partially blind and is constantly pacing-vet and i are not sure why he is pacing-anxiety???giving a little tranquilizer—-i have had many,many animals but never had this problem-i would suggest tests for high blood pressure and thyroid tests-bb

Oct 05, 2011 Manx cat with dialated eyes also
by: Dalene

I have a manx that doesn’t appear to have slits for eyes they are round like a humans. Is this what they consider dialated? Her eyes are always like this they do not go into slits ever. She is an indoor cat and has been since kittenhood. That I know of she was not inbred or neglected as far as her regular visits to a veterinary. She appears to see just fine, plays with toys, jumps up on tables accurately and even follows a laser light on the floor. I am very curious about this condition with her eyes. She does have very light blue eyes.
Can I get more information about this condition?

Dec 21, 2010 My 8 month old kitten has both eyes dilated since birth
by: april

My kitten spooky, said to look like an havanah brown, but not. She was rescued from a cat hoarder and sadly her siblings are already having litters of their own. all of the 20-30 cats this woman has now she cant care for and they all have dilated pupils. This shows that whatever it is its hereditary. She was treated at 8 weeks old for ear mites and an umbilical lump on her belly, which is apparently commen for constant pregnancies of the mom cat. Shes now perfectly healthy, vaccinated and neutered but her eyes are both dilated permenently and the vet shows no concern with it. She can see partially in both eyes but the best in the right eye per light tests performed but she plays with a toy and can’t find where it landed. She gets on tables, counters and everywhere which is typical but i’m concerned about treatment. I don’t want whatever it is to get worse over time, i want to treat the issue and can’t get anyone to show interest in soving it. Also another trait her and all 30 cats in that house are polydactyl cats, they have extra toes on each paw. she has an extra toe on each paw that makes them look like boxing gloves which per the internet is just a genetic trait that is passed onto each litter. the inbreeding is making me nervous on her future. any one can help i’d appreciate it..

Sep 02, 2010 bilateral dialatd pupils
by: Linda

My cat is 5 years old and in low or medium light her pupils look like round saucers. Her eyes have been that way since she was a kitten. Her pupils do contract to slits in a bright sunny room. Over the past year I noticed that she is having vision problems up close. She will run into walls especially if they are painted white. She no longer chases strings or plays with toys. I spoke with a vet that specializes in cats and she did not seem concerned. She offered a referral to a specialist and that was her only suggestion. No tests were done. Anyone having similar issues?

Aug 16, 2009 Cat Dilated Pupils
by: susie

Hi all,

I am about to adopt a kitten with dilated pupils. He is not blind and responds well to objects in front of him and while playing. Derek, have you found anything about your cat?


Jun 17, 2009 My kitty also has a dilated pupil…one eye only.
by: Anonymous

I pointed this out 2years ago to my vet, who specializes in cats, and she was likewise puzzled. She said if the kitty had hypertension he would have it in both eyes and that you would see small pinholes in the iris. We do not, and it is only in the right eye. She seemed unconcerned and did not prescribe any medication, and also assured me he was NOT blind in that eye.
As time went on, I changed vets for various reasons, and our new, and very thorough vet, said he does have glaucoma in that eye (only), he probably has been blind in that eye all along, and it did not appear to be hypertension. The intraoccular pressure was quite high when she first saw him, she prescribed drops which brought it down almost immediately, but after 6 months it was back up, so we are now on a different medication. She consulted with a feline ophthamologist on the subject. You might want to see if you have one in your area and check it out. Your kitty may have early stages of glaucoma, which is what I believe at this point, mine did.
Good luck to you.

May 15, 2009 Response to last comment
by: Anonymous

Hi Derek, Pleasure, but as I said a good vet is the answer. There will be an underlying problem that might be quite serious. The dilated eyes simply being one symptom. There are other possibilities. I would have thought fairly quick treatment is required. Good luck to your cat and to you.


May 15, 2009 My Cat has Dilated Pupils
by: Derek Jordan

Thank you for your comments and advice Michael.
I have an appointment with the vet again in 10 days, if I cannot get a satisfactory answer from him I will consider changing my vet. I had to point out the problem to him and I must admit he seemed puzzled. I do not know what a low sodium diet would consist of.

Thanks again


Michael Broad

Hi, I am 70-years-of-age at 2019. For 14 years before I retired at 57, I worked as a solicitor in general law specialising in family law. Before that I worked in a number of different jobs including professional photography. I have a longstanding girlfriend, Michelle. We like to walk in Richmond Park which is near my home because I love nature and the landscape (as well as cats and all animals).

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