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Ask Dr. Michael Salkin Your Own Question
Dr. Michael Salkin
Dr. Michael Salkin, Veterinarian
Category: Pet
Satisfied Customers: 29770
Experience:  University of California at Davis graduate veterinarian with 45 years of experience
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Is it normal cat to have one pupil very sligthy bigger

Customer Question

Hi. Is it normal for a cat to have one pupil very sligthy bigger than the other one? About 2mm or so. My cat seems healthy otherwise
Submitted: 2 years ago.
Category: Pet
Expert:  Dr. Michael Salkin replied 2 years ago.
Hi Susan, This is called anisocoria and it has quite a few possible etiologies. The two most common causes are the leukemia (FeLV) virus and the spastic pupil syndrome - a condition unique to cats in which owners report anisocoria, which may sometimes be transient and independent of ambient light levels. Clinically, cats with this syndrome appear to be healthy, are visual, and have no ocular abnormalities beside unusual behavior of the pupils. Unfortunately, many affected cats test positive for FeLV at the initial presentation but not all which confounds the diagnosis.Anisocoria also results from primary iridal (iris) disease - any inflammatory process causing miosis (an abnormally small pupil); and primary neurologic disorders involving cranial nerve III and Horner's syndrome.The initial database should involve testing for FeLV and a complete ophthalmic examination including menace response, dazzle, palpebral, pupillary light, and vestibulo-ocular reflexes. Fluoroscein staining of the cornea should be performed looking for corneal trauma and intraocular pressure should be measured (the elevated pressure of glaucoma will enlarge the pupil (mydriasis) and the lowered pressures of uveitis will make the pupil smaller (miotic).Much of the above is beyond the capability of many generalist vets so your vet vet may recommend referral to a board certified veterinary ophthalmologist. Please see here: www.acvo.orgPlease respond with further questions or concerns if you wish.
Customer: replied 2 years ago.

I checked them again and they seem normal. I guess i was checking from the wrong angle. She was checked about a month ago with no issues. She also got tested for feline leukemia few months ago and was negative. I made an appointment with a for thursday just in case.

Expert:  Dr. Michael Salkin replied 2 years ago.
That's good enough for me. Thank you for letting me know.
Expert:  Dr. Michael Salkin replied 2 years ago.
("...with a specialist veterinary ophthalmologist for Thursday..."?)
Customer: replied 2 years ago.

No. Just my regular vet. I just hope she is ok :(

Expert:  Dr. Michael Salkin replied 2 years ago.
Ah! That's a good start particularly if the vet is handy with an ophthalmoscope because the entire eye needs to be examined including a fundic exam (the posterior segment/retina).
Customer: replied 2 years ago.


Pic of my cat's eyes. Normal, right?

Expert:  Dr. Michael Salkin replied 2 years ago.
I regret that I can't open that file. You can upload a photo by using the paperclip icon in the toolbar above your message box (not if you're using the chrome browser) or you can use an external app such as or
Customer: replied 2 years ago.

Expert:  Dr. Michael Salkin replied 2 years ago.
Thank you. I don't see a difference between one pupil and the other. The lighting isn't good, however. The same amount of light should reach each eye for pupillary assessment to be most accurate. Cute puss, though.
Customer: replied 2 years ago.

Thanks! She is my angel, she came to me when I needed her the most. I think it was the lighting. I keep checking her in different parts of the house ans I get normal results. I think i am an overprotective mom :)

Expert:  Dr. Michael Salkin replied 2 years ago.
You're allowed to be. And I get to speak with you a lot because of that.