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Why is my cat's third eyelid showing halfway over both eyes in light?

Updated on September 23rd, 2025

Pet's info: Cat | Domestic Shorthair | Female | spayed | 1 year old | 11.7 lbs

My cat has no fever or eye discharge, normal eating, normal bowel, but nictitating membranes are halfway over both eyes in light and go away in low light. One membrane is a little red but no eye discharge, no fever. Eyelids good color. Gums good color. Any ideas? Blood work not back yet. Cat is about 1 year old.

1 Answer

Most Helpful Answer

Laura Johnson VMD

Answered By Laura Johnson VMD

Veterinarian

Published on June 15th, 2018

Hi, thanks for using Petco Pet Education Center, formerly Petcoach!

I can think of 2 things: 1) uveitis which is inflammation of the uveal structures in the eye. It can cause light sensitivity. It is diagnosed by measure the intra-ocular pressure. It would come back low. Causes of uveitis in cats is trauma to the eye, feline leukemia, infection, metabolic disease, etc. 2) Haws syndrome. Which is GI disease. In a young cat I would be sure he gets dewormed regardless of a normal stool sample. Consider a dietary change if deworming doesn't resolve the issue.

I hope Sofia does well!
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