Feline Cat Behavior Changes With Uneven Pupils

Your kitty's eyes can signal illness or injury, so peer away!
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Your kitty’s eyes are huge and beautiful ... and the pupil of one of her eyes is larger than the other. Your cat might also be tilting her head or pawing at her eye, as if it hurts her. If you notice she’s confused, get her to the vet immediately.

Anisocoria’s Potential Causes

When your kitty has two differently sized pupils, this is called anisocoria. Even if she’s not showing any other symptoms, it’s important to get her seen by your vet as soon as possible. Your feline gal might have a head injury that’s causing one pupil to expand or shrink abnormally. This condition can cause some noticeable behavioral changes in your kitty as she tries to adjust to changes in vision or head and eye pain.

She might be suffering from an abnormally developed iris, which is the colored part of her eye; she might have scar tissue buildup in her eye or a tumor -- yikes, this is serious! Or she could be developing a condition in which the pressure in her affected eye is going up. She might have inflammation in the front part of her eye.


Once you’ve noticed the difference in her pupil sizes, look for other symptoms. These could include head or eye pain. Your kitty might tilt her head to one side or paw at the affected side of her head. She might be showing signs of confusion, which could suggest a possible head injury. All of these symptoms are important.

If your vet diagnoses a head injury, a tumor or a buildup of pressure in one eye, these have to be treated right away. Taking a “wait and see” approach isn’t a good idea in this case.

Other Signs of Anisocoria

If you like gazing into your kitty’s eyes because of how gorgeous they are when she’s healthy, keep doing so now that you’ve noticed her condition. Look for these other signs: a droopy eyelid over her affected eye or squinting behavior. Your cat might rub at her eye, indicating that it’s not feeling comfortable. She might be less active than she normally is. The cornea, which is the clear lens over her eye, might be cloudy or have a bluish tinge to it, or the white of her eye might be reddened. All of these other symptoms come from other causes of her anisocoria, so take her to the vet for the correct diagnosis.


When you take your kitty-girl in for an exam, the vet will give her a complete physical. He’ll want to examine her affected eye and run some tests on her. These could include tests to measure the intraocular pressure inside her eye as well as her tear production. He’ll also want to look for evidence of injury to her cornea, so he’ll instill an eyedrop that stains her cornea with a fluorescent dye.

As he continues looking for the cause of your cat’s anisocoria, he’ll take scrapings of the surface of her eye. He may refer your kitty to a veterinary ophthalmologist for more specialized diagnostic work and a possible diagnosis. Expect him to take blood, because he’ll need to consider a condition such as feline leukemia.


Relax, because this condition can be treated. The treatment your vet selects is affected by the cause of her uneven pupils. When he finds out what’s causing her condition and discomfort, he’ll discuss the best treatments with you. However, depending on the cause of her condition, her recovery may be partial or it might be complete. She might also need medication over the long term to control whatever caused her anisocoria.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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