Optic Nerve Hypoplasia
Optic nerve hypoplasia is a rare neurological disease in which one or both optic nerves are underdeveloped, preventing the animal from seeing normally. Any dog or cat can have optic nerve hypoplasia, though some dogs are thought to inherit the condition. It can occur in one or both eyes, and an owner might notice that his pet doesn’t see well or might not notice any vision impairment at all. There is no treatment for the disease, and affected animals will live a lifetime with a degree of sight impairment.
OverviewThe optic nerves — located at the back of the eyes where they establish a direct connection to the brain — are necessary for vision. Optic nerve hypoplasia is a condition that uncommonly affects the optic nerves of cats and dogs. In this disorder, a failure of the optic nerve to develop fully leads to a variable degree of vision reduction (or even blindness) in one or both eyes.
In some cases, the eyes of affected animals are otherwise normal. In other instances, the eyes are malformed in a variety of ways. In all cases, the optic nerves are smaller than they should be, and contain fewer nerve axons. Beyond an understanding of its genetic origins, exactly how this disease occurs is not well understood.
In kittens, optic nerve hypoplasia may occur as a result of panleukopenia (feline distemper) infection while they are in the uterus. These animals will typically show other neurologic signs as well.
Symptoms and IdentificationDiagnosis usually occurs incidentally in the course of normal ophthalmic evaluation or because vision impairment is suspected. The animal may exhibit previously unrecognized evidence of vision impairment in one or both eyes, display dilated pupils in the affected eyes, and fail to respond normally to light. Confirmation of the diagnosis occurs through fundoscopic examination (looking at the back of the eye with a lens) where the presence of a smaller-than-normal optic disc may be visualized.
Severely affected (completely blind) animals are typically diagnosed soon after birth.
Affected BreedsOptic nerve hypoplasia appears to be genetic in Poodles.
TreatmentNo treatment is available for this condition.
PreventionAffected and carrier individuals should be removed from the breeding pool.
This article has been reviewed by a Veterinarian.