Early cataracts secondary to PRA
What is Progressive Retinal Atrophy (PRA)?
PRA is a collective term used to define a number of genetic disorders in dogs that lead to retinal degeneration. These are hereditary diseases, meaning that dogs inherit the genes that cause the disease from their parents. Purebred and mixed breed dogs can be affected, with toy poodles and Labradors being especially common. Most of the diseases are autosomal recessive, meaning a dog has to have both copies of the problematic gene, but some are autosomal dominant or sex-linked. The actual genetic mutation is known for many breeds, and can be tested for.
What are the signs of Progressive Retinal Atrophy?
Onset of this disease is gradual, and usually signs are not apparent to the owner until the disease is quite advanced, which can occur at a young or older age. Breed and the specific genetic mutation play a role in how quickly the disease progresses. Nyctalopia, or trouble seeing at night, is often the first noticeable sign. This occurs because the rods of the retina are affected first with most forms of PRA, and the rods are important for seeing in the dark.
How is Progressive Retinal Atrophy diagnosed?
A suspicion of progressive retinal atrophy can be made based on ophthalmic exam findings. The main finding is bilateral, symmetrical retinal degeneration. A retinal function test called an electroretinogram (ERG) can also confirm decreased retinal function, but usually changes on examination are obvious enough that the ERG is not necessary. Genetic testing for the disorders is available through various veterinary laboratories, and can be important to breeders who want to ensure that the disease is not present in their lines.
What is the treatment for Progressive Retinal Atrophy?
There is unfortunately no treatment for any of the forms of PRA in dogs at this time. Gene therapy has recently been successful to treat some similar genetic retinal diseases in people, and this may eventually become available to dogs in the future as the technology improves. The good news about PRA is that it is not painful to dogs and many adjust well to their blindness, especially because it is gradual in onset. Most owners of dogs with PRA find that their pet functions very well and has a happy life. Many dogs with PRA will eventually develop cataracts as a consequence of their disease. The cataracts can make the eyes look cloudy, but these dogs are not candidates for cataract surgery because of the retinal degeneration.