Progressive retinal atrophy (PRA) is a genetic condition that results in the degeneration of the retina. The disease ultimately causes the loss of vision in low light conditions such as at night, then progresses to limit vision during the day.
A dog's retina is fully developed by 6 weeks of age. Progressive Retinal Atrophy can occur before that time (early onset PRA) or after several years (late onset PRA).
Currently, there is no treatment for PRA. Since the disease progresses slowly, dogs suffering from the condition have time to adapt to the changes in sight; dogs tend to adjust fairly well.
This condition has been seen in over 100 breeds of dogs. Some breeds are more susceptible to the problem. Recent advances in DNA testing promise to help breeders select dogs that are not carriers for the disease.
Symptoms and Diagnosis of Progressive Retinal Atrophy in Dogs
The first symptom of PRA is a condition called night blindness where your dog can see during the day, but has trouble at night. This is followed by the loss of vision during the day.
The age that this occurs varies by the type of PRA your dog has. Symptoms include a noticeable enlargement of your dog's pupil and an increase in the reflection coming off the eye.
Other problems include cataracts which is a result of the PRA (vs. the cataracts causing the vision loss).
Your veterinarian will do a vision assessment including having your dog walk through an obstacle course to see if he or she can navigate around objects that they haven't seen before.
Problems impact both eyes equally.
Types of Progressive Retinal Atrophy in Dogs
Rod Cone Dysplasia
There are 4 breeds that are susceptible to this kind of PRA:
- Irish Setter
- Cardigan Welsh Corgi
- Rough Collie
Symptoms are similar to those described above including cataracts as a secondary condition. The disease can start as young as eight months of age leading to complete blindness by age 12.
Progressive Rod Cone Degeneration (PRCD)
Most breeds are affected by this type of PRA, including retinal atrophy in poodles. This condition occurs later in a dog's life but the exact timing varies by breed and within breeds.
Breeds affected include:
- Miniature Poodle
- Toy Poodles
- Labrador Retrievers
- English Cocker Spaniels
- American Cocker Spaniels
- Portuguese Water Dogs
- Chesapeake Bay Retrievers
- Australian Cattle Dogs
- Nova Scotia Duck Tolling Retrievers
The condition is diagnosed using DNA testing which identifies dogs that do not have prcd, carriers and those that are affected by the disease or are normal.
This type of PRA is found in two breeds:
X-Linked PRA tends to be worse for the Samoyed than the Husky.
This version of the disease impacts the Mastiff breeds.
Progressive Retinal Atrophy: An Overview
Simon M. Petersen-Jones, DVetMed, PhD, DVOphthal, DECVO, MRCVS
Department of Small Animal Clinical Sciences
Michigan State University
East Lansing, MI, USA