Anisocoria in 15 year old cat.

Dr. Marie replied:

What you are describing with the pupils being different sizes is called anisocoria. There are several possible reasons for anisocoria in a cat. What your vet is describing with "something in the brain" certainly can be true. Anisocoria can be due to a tumor affecting the optic nerve which travels from the eye to the brain. It's hard to diagnose this type of thing without doing expensive tests like an MRI or a CT scan.

However, a tumor should not really cause a film to cover the eye. If the film is on the outside of the eye then it sounds like there could be damage to the cornea. Another possibility is an immune mediated problem that is causing the cells on the cornea to react.

If, however, the film is more inside of the cornea she could have a condition called uveitis. There are many possible causes for uveitis but it always means that something serious is going on inside the body. Viruses like Feline Leukemia or FIP can do this but these are not common in a 15 year old cat. A variety of other illnesses can do this as well.

Glaucoma could cause issues like this as well. Glaucomia is a buildup of pressure in one eye. It is quite painful but cats will often show no outward signs of pain.

If the film is something new it may be worthwhile to have your vet take a look as this may give him a new clue as to what is going on. Another option is to ask your vet for a referral to a veterinary ophthalmologist as these vets are used to seeing unusual conditions in eyes.

It definitely sounds like something that is worth checking out. Whether or not it is causing her discomfort is debatable, but my guess is that this could be uncomfortable for her.

Dr. Marie

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