My Cat has Dilated Pupils (always)

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?


Dilated cat pupils
Dilated cat pupils (this is a photoshopped image by me to illustrate the page. Original photo by Ged Carroll
Two useful tags. Click either to see the articles:- Toxic to cats | Dangers to cats

Hi Derek: I am not sure that you have described the problem accurately. If the pupil is wide open it is dilated. Perhaps you mean that the pupil 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.

Iris not responding to light input

If the iris is not responding to different light levels by closing and opening the pupil it might indicate that your cat is blind or partially 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. It appears that this is what is happening with your cat but I am not a veterinarian. Seek veterinary advice please.

Hypertension can damage the blood vessels in the retina and it can cause the retina to detach which in turn can cause partial or complete blindness on my understanding of this disease.

Any disease that reduces the sensitivity of the retina to light impulses such as retinal atrophy or a disease which affects the optic nerves or that part of the brain which processes information from the optic nerve (e.g. brain trauma) can produce visual disturbance including blindness which can cause the operation of the irises to change which in turn can lead to the pupil being in an always dilated position.


High blood pressure (hypertension) is one of the most common causes of retinitis which is a disease of the eye in which inflammation of the retina leads to the degenation and destruction of the light receptors. There are various causes including toxoplasmosis, feline infectious peritonitis, lymphoma, and systemic fungus infections but, as mentioned, one of the most common causes is high blood pressure.


Shining a light into your cat’s eyes is not a guaranteed test of whether they are partially or completely blind. It is not exact enough because the pupil may become smaller because of a reflex action. In which case it doesn’t tell you if the brain is receiving visual images.

Perhaps a more general way to diagnose if a cat is blind is through their behaviour and activity. Activities that require good body coordination such as jumping from a sofa to a chair may show that the cat’s abilities are impaired. And sometimes in a dimly lit room cats with limited or no vision may bump into furniture. They may hold their noses close to the ground and feel ahead with their whiskers which are pointed forward.


Sometimes, with older cats their eyesight might fail soon after they become deaf. They then have to rely more on memory to find their way around their home. Many blind cats get along quite well because they are familiar with the surroundings and they can use their other senses. Everything in the home should be kept in its place this reason.

Of couse 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, 2011Review 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, 2011dilated 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, 2011Manx 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, 2010My 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, 2010bilateral 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, 2009Cat 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, 2009My 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, 2009Response 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, 2009My 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


6 thoughts on “My Cat has Dilated Pupils (always)”

  1. Miss Ashleigh, I hope your cats eyes are not from inbreeding.. I have a 16 yr old male mackerel tabby. this past january he had a runny eye, vet treated it with drops. two weeks later he had a huge lup on his brow, it was soft-like and spongy. vet said it was cancer and my husband wanted an antibiotic. (couldn’t hurt) . one week later the lump was gone. he is still with us today except now he has fixed and dialated pupils.. even in the light. the vet has no concern with this.. I do!!.. he stopped playing and I have to point and tap for him to get his food. vet checked the eyes and examined the optic nerves in the back and are clear… . my cat had no inbreeding and was in a litter of 3 kittens that burned in a fire except for him.. he is a very special cat. and has fought off a lot of medical problems that the vet said he would never live thru. he is getting weaker now but my concern is that he cant see and is scared. he is always in my face to smell my lips when I talk to him.. I wish I knew what the dilated pupils ment…

    • Marianne, your story is touching. You have a wonderful cat. I find it strange that your vet found permanently dilated pupils to be OK. That can’t be right surely? The brain closes down the iris in bright light so there is some sort of neurological problem. There has to be even if he is not blind. Has he been tested for blindness? Thanks for sharing.

  2. I realize this post is old, but just in case people are still reading…
    I have a 7yo cat who was the runt. She weights ~3.5lbs. A mini-kitty. Bottle-fed as her ma didn’t allow her to feed. I took her in after living with her for a year as the roommate was just going to ‘let her go in the woods.’
    She is highly skittish (more so than most cats,) and it’s taken me all these years to gain her trust. She sleeps on me & kneads, etc, and is the sweetest, and weirdest, cat I’ve ever had.
    I found out a few years ago that she was ‘a baker,’ as we affectionately call her, instead of inbred ( mother/son.) She goes feral when taken out of her environment, even vets are scared of her; her tone gets low & she won’t allow touching & forgets who her protectors are.
    As she’s so tiny, we’ve always referred to her as being ‘all eyes and whiskers.’ It wasn’t until about a month ago when we took in a stray (doppelgänger, but growing,) that I realized her constantly enlarged pupils weren’t normal. (@ first I thought something was wrong with the other cat.) Then it slowly dawned on us that her vision may be compromised. She’s clumsy, but so are we, so we always joked she took after us.
    Big, round, black pupils. All the time. When calm, loving, active, spazzing, half-asleep.
    I’m afraid the vet brings so much trauma (lasts for days. & vets have to ‘gas her’ to get near,) so I don’t subject her to visits unless she’s sick, which she rarely has been. She does not adapt to change well. She seems to be in good health, and is a loving sweetheart, and I am also very poor right now, so unless she showed signs of illness, I wouldn’t be able to take her to the vet (& she’s ‘flagged’ at local vets.)
    However this’s pupil thing has me questioning her vision. She doesn’t walk into walls but she misses jumps & is timid navigating.
    Any ideas? Could this be from the inbreeding & not a sign of blindness? She’s always been this way, since she was months old.


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