Iris Atrophy

Iris Atrophy is an age-related thinning of the iris that commonly occurs in cats and dogs.  The iris is the colored tissue inside the eye that surrounds the pupil (which is a circular structure in the dog and a slit-like structure in the cat).  The iris has a muscle that allows the pupil to become smaller (like a camera aperture) when exposed to light to protect the retina in the back of the eye.  However, iris atrophy will occasionally result in thinning of this muscle, which can eventually prevent the pupil from constricting.  In these cases, the pupil may remain dilated, or large.  In addition, iris atrophy can occasionally result in a “moth eaten” appearance to the iris.

Iris Atrophy is typically not a problem and rarely results in changes to a pet’s functional vision.  It is non-painful.  Some animals will exhibit sensitivity to and squinting with bright light when the iris atrophy is significant.  Since this condition may be mistaken for a potentially serious problem, such as glaucoma or a neurologic condition, an examination with your pet’s veterinary ophthalmologist may be necessary.