Retinal degenerations

Retinal degenerations may be inherited or occur spontaneously. The Electroretinogram (ERG) is the test of choice, when retinal degeneration is suspected. This test is similar to the Electo-Cardio-Gram (EKG), where electrodes are employed to pick up electric charges from the heart. In the ERG a flash is used to activate the retinal photoreceptors (discharge) and electrodes pick up the electric charges in MiliVolts.

If you suspect your pet/animal may have a retinal disease/degeneration you can contact your veterinarian to arrange a referral to the Animal Medical Centre Referral Services, Manchester, to arrange a consultation with Dr Thomas Ffrangcon Evans.

cats, dogs,

Cats

Retinal degeneration that is not linked to high blood pressure (hypertension) is uncommon in the cat. In Abyssinian and Siamese cats a progressive retinal degeneration (PRA) has been described in young cats. I have seen one Somali cat with PRA similar to that described in the Abyssinian. Taurine is an essential aminoacid to the cat, this meens that cats cannot synthesize the aminoacid by themselves and the Taurine in the diet is important. Cats fed diets deficient of Taurine (eg. vegetarian diets) are at risk of developing Central Progressive Retinal Atrophy (CPRA). Since the 80'ies all commercial cat diets have high levels of Taurine and most clinical cases of CPRA usually have a history of hand rearing kittens with cows milk (deficient/low in taurine). Only commercial milk substitutes such as Cimicat etc. should be used for hand rearing kittens.

PRA in a Somali Cat (Early changes)

The endstage of PRA and CPRA looks very similar in cats. The retina is destroyed, very reflective, all retinal vessels have gone and the optic disc is dull and gray.

Dogs

In dogs there are several types of retinal degenerations that have been described. The most common name is PRA (Progressive Retinal Atrophy) and implies that the retinal degeneration is progressive and ends in vision loss. In breeds, where the retinal degeneration has been studied.

Some breeds of dogs are commonly affected and these include: Poodles, Cocker Spaniels, Irish Setters, Labrador Retrievers.

Testing of some breeds for PRA-genes is possible and more information is available at the website www.optigen.com.

No treatment is possible for PRA in dogs, but currently some research is going into doing retinal transplants and this may become a clinical possibility in the future. Some studies in the human types of retinal generations (Retinitis Pigmentosa) have shown a tendency of prolonging vision when treating with antioxidants (Vitamins) and Zinc. I currently advise some dogs with early signs of PRA to try this therapy because there are no sideeffects and prolongation of vision is a possibility.

This section of mammaleye.com is written for Owner's of patients under my therapy. Others may of cause gain knowledge about eye diseases in pets. Remember that other veterinary ophthalmologists may wish to treat diseases of the eye in a different way than myself.

If you as an owner want further information (scientific) about eye diseases then have a look at http://www.mammaleye.com/prof.htm or go to pubmed and do a search on Medline - the main resource of scientific information for the whole medical profession.