Imaging like X-rays and ultrasounds may also be useful in achieving a diagnosis that explains the anisocoria. When a veterinarian examines a cat with anisocoria, they will carefully inspect both eyes, checking neurologic reflexes and looking for other abnormalities that may be too subtle to notice at home or with the naked eye.ĭepending on the results of the physical exam, they may recommend bloodwork, including tests for organ function or certain infections. How Vets Diagnose the Cause of Anisocoria in CatsĪnisocoria is a symptom that can lead to the diagnosis of an underlying disease. Take pictures of your cat’s eyes in the abnormal state for the veterinarian, because occasionally, their eyes can go back to looking normal by the time a vet can examine them. Some causes of anisocoria can progress rapidly, so it’s important to have your cat examined by a veterinarian as soon as you notice the abnormal pupil size. Go to the emergency vet if you notice that one of your cat’s pupils is wider than the other.Īlthough chances are good that the underlying cause is not a true emergency, in this situation, it’s better safe than sorry. What to Do if Your Cat’s Pupils Are Different Sizes Older cats are also more prone to cancer, and cancer within the eye can cause anisocoria in cats. Neurologic disease can contribute to either dilated or constricted pupils in cats.Įating certain toxic plants can cause one pupil to be larger than the other.Ĭertain viral, fungal, and parasitic infections can cause anisocoria in cats, and they are more common in cats that have access to the outdoors or were once strays. The pupil may also constrict inappropriately due to inflammation in the eye or painful conditions like corneal ulcers. Pupils can abnormally dilate due to conditions like glaucoma or damage to the retina in the back of the eye. Here are some of the causes of anisocoria in cats:ĭiseases inside and outside the eye can lead to anisocoria in cats. It is difficult to provide an exhaustive list of all the causes of mismatched pupil sizes in cats because there are so many. Therefore, if you notice your cat’s pupils are different sizes, even occasionally, a veterinary exam is important to uncover the cause. While dogs and people can develop “idiopathic” anisocoria, in which the pupils are occasionally different sizes for no reason at all, this is much rarer in cats. Can Anisocoria in Cats Be Fatal?Īlthough anisocoria itself is not fatal, nor even painful in most cases, the underlying cause is the more important issue. The abnormal eye may have either the smaller or bigger pupil, depending on the cause. When a cat’s pupils do not dilate or constrict appropriately, it can indicate a problem in one or both eyes. A cat’s pupils do this by getting wider or narrower in response to changes in the brightness of their environment. The function of pupils is to control the amount of light entering the eye. What Is Anisocoria in Cats?Īnisocoria in cats is defined as a significant difference in the pupil size of each eye. 12:85-89.Go to the emergency vet if you notice that one of your cat’s pupils is wider than the other. Physiologic anisocoria under various lighting conditions. Steck RP, Kong M, McCray KL, Quan V, Davey PG. Unilateral mydriasis due to Angel's trumpet.

28(3):236-7.Īndreola B, Piovan A, Da Dalt L, Filippini R, Cappelletti E. Transient anisocoria caused by aerosolized ipratropium bromide exposure from an ill-fitting face mask. False negative apraclonidine test in two patients with Horner syndrome. Horner's syndrome, Pseudo-Horner's syndrome, and simple anisocoria. Topical apraclonidine in the diagnosis of suspected Horner syndrome. A flow chart for sorting out the anisocorias. Sex-specific lateralization of contraction anisocoria in transient pupillary light reflex. Measurement of pupil size with the video screen of an infrared autorefractor.

Image of unequal pupil size