Degeneration of the Iris in the Eye in Cats

PetMD Editorial

Published Apr. 24, 2010

Iris Atrophy in Cats

Iris atrophy refers to the degeneration of the iris, the colored part of the eye that surround the black center (or the pupil). This medical condition can affect cats of all ages and breeds, but appears to be more common in cats with blue irises. There is also a secondary type that is due to chronic inflammation or high intraocular pressure resulting from glaucoma.

Symptoms and Types

Vision is not usually affected by iris atrophy, but there may be some sensitivity to light. Other typical symptoms associated with this of disorder include:

Incomplete pupillary light reflex, accompanied by a normal menace response (the reflex to close the eyes when a finger is stabbed toward the eye)
Unilateral — may note anisocoria (unequal pupil sizes)
Irregular, scalloped edge to the pupillary margin
Thin or absent areas of the iris on transillumination
Strands of iris occasionally remain, spanning across portions of the pupil
Holes within the iris stroma — black spots that may resemble additional pupils
Swelling (edema) of the cornea

Causes

Normal aging
Uveitis (inflammation of the uvea portion of the eye)
Glaucoma

Diagnosis

Your veterinarian will perform a thorough physical and ophthalmological exam on your cat. The initial goal will be to differentiate iris atrophy from congenital iris anomalies, as there are a variety of other eye issues that can be the cause of the symptoms, such as ris aplasia (failure of the iris to develop normally), iris hypoplasia (underdevelopment or incomplete development of the iris), iris coloboma (a complete, full-thickness area of lack of development of all layers of the iris), and polycoria (when more than one pupil is present in a single iris within the animal's eye, each with the apparent ability to constrict).

Treatment

Iris atrophy is not reversible, so much of the treatment is designed to target the underlying disease that has caused it, or to halt the progression of the disease.