Progressive Retinal Atrophy (PRA)
a degenerative disease of the retina
What is it?
Think of the eye as a camera. The front of the eye is like the lens of the camera and the back of the eye, where the retina is located, is like the film in a camera. In PRA the film (retina) is going bad. Like a camera with bad film an eye affected by PRA does not produce a usable image. There are many forms of PRA but they all result in gradual vision loss.
What causes it?
Generally, PRA is an inherited disease. It is found in all breeds and even mixed breeds. In most breeds, the disease is inherited by simple autosomal recessive mode. Autosomal recessive inheritance requires one bad gene from the mother and one from the father. Neither father nor mother has to have the disease but may simply be carriers.
What are the symptoms?
Historically affected dogs will have vision problems initially in dim light the vision loss progresses to abnormalities in all light conditions. In some dogs that do not metabolize fats well, feeding a high fat diet or high fat snacks can cause excessive fat in the bloodstream (hyperlipidemia). The hyperlipidemia slows blood flow through the retina and causes less oxygen to be carried to the retina. Numerous episodes of hyperlipidemia induced retinal hypoxia can cause atrophy of the tissue and vision loss.
What is the treatment?
Currently there is no treatment for PRA. Dogs will generally adapt to their vision loss easily especially with help from their owners. A resource we suggest is Caroline Levin’s book ‘Living with Blind Dogs’. The book has many training techniques that may make the transition through vision loss easier for the patient and the owner.
A cataract, opacification of the lens, is the most common secondary problem to PRA. Removal of the cataracts is not usually pursued since removal of the cataract does not improve vision. Occasionally, Dr. Hodgson will remove a cataract to prevent lens induced uveitis and secondary glaucoma. Since the disease is most likely inherited, an affected dog should never be bred.