Progressive Retinal Degeneration In Dogs
Progressive Retinal Degeneration (PRD) is widespread throughout purebred dogs, with over 85 breeds known to have contracted the disease to date. It has been noted that any bread of dog can be affected by PRD.
The disease affects the retina, which is the innermost layer of the eye. It is located in the back half of the eye, and is composed of specialized nervous tissue that transmits the image viewed by the eye to the brain for interpretation.
The first sign of PRD is a loss of night vision, followed later by the loss of day vision. Because dogs do so well with very limited vision, owners often don't detect the disease until it is quite advanced. In some dogs, (e.g. Irish Setters) the loss of both day and night vision occurs simultaneously. Occasionally, owners will note that dogs have trouble seeing moving objects. The disease may also first be detected when the animal leaves its familiar environment (e.g. on vacation), when bumping into objects or hesitancy may be noted.
As the disease progresses, pupils may remain dilated regardless of changes in light, Often, because the pupils are dilated, owners may notice cataract formation. The disease is not related to cataracts, but cataracts may form secondary to the disease. It is a retinal problem for which there is no treatment.
To diagnose the disease, an ophthalmoscopic examination is done. Early subtle changes are best detected by a veterinary ophthalmologist.
Good breeders routinely screen their breeding stock. However, as PRD can be a late onset disease, many offspring may have already been produced before the disease is detected in the parents. However, NO offspring from affected dogs should be used for breeding purposes. This is thought to be a simple autosomal recessive inheritance, so that carrier dogs cannot be detected.
Any dog with mature cataracts should be screened prior to surgery for a functional retina. This is done by electroretinography (ERG). It is pointless to remove cataracts if the dog is retinally blind. Occasionally, a luxated lens may be removed in a dog that is blind in an attempt to prevent glaucoma.
For more information on PRD or other eye problems, please see your veterinarian.