Spastic pupil syndrome - a syndrome that may be associated with feline leukemia virus infection.Congenital defect of the iris, in which the iris tissue does not develop properly.Iris atrophy (a decrease in the amount of tissue within the iris) usually a degenerative change associated with aging.Scar tissue formation between the iris and the lens (called posterior synechia), a condition that may develop following uveitis.Uveitis, or inflammation of the interior of the eye (the pupil in the affected eye will usually be constricted).Glaucoma, a disease in which there is increased pressure within the eye (the pupil in the affected eye will be dilated).Disease or injury to the brain or to the nerves running to the affected eye, such as Horner’s syndrome.In some cases, the abnormal pupil may be the one that is smaller and in other cases the abnormal pupil may be the one that is larger.Īnisocoria is a sign of a disease of condition, therefore there can be several different causes, including: What is anisocoria?Īnisocoria is a condition in which the pupils of the cat's eyes are different sizes in other words, one pupil is larger than the other. The pupil constricts or dilates (enlarges) according to the amount of light that enters the eyes, with both pupils normally dilating in dim light and constricting in bright light. In cats, the pupil is an elliptically-shaped opening in the middle of the iris that allows light to pass through the eye to the retina.

Dilated pupil