PRA, or Progressive Retinal Atrophy, is not a gene itself, but rather a group of inherited eye diseases that cause progressive blindness in dogs. These diseases affect the retina, the light-sensitive tissue at the back of the eye, leading to gradual vision loss. Various genes can cause different forms of PRA.
Here's a breakdown of what that means:
- Progressive: The disease worsens over time.
- Retinal: The retina, which is responsible for capturing light and transmitting visual information to the brain, is affected.
- Atrophy: The retinal cells degenerate and waste away.
How Does PRA Cause Blindness?
The retina contains two types of light-sensitive cells: rods and cones.
- Rods: Primarily responsible for vision in dim light (night vision). Rod degeneration often leads to night blindness as an early symptom of PRA.
- Cones: Responsible for vision in bright light and color vision. Cone degeneration leads to daytime vision loss and eventually complete blindness.
In PRA, either rods or cones (or both, depending on the specific form of the disease) progressively degenerate, ultimately leading to blindness.
Genetic Basis of PRA
PRA is caused by various gene mutations. Different breeds are predisposed to different forms of PRA, each linked to a specific gene. These genes encode proteins crucial for the normal function and survival of retinal cells.
Breeds Affected
While PRA can affect almost any dog breed, some breeds are more commonly affected, including:
- Labrador Retrievers
- Poodles (especially Miniature and Toy Poodles)
- Cocker Spaniels
- Australian Cattle Dogs
Crossbreed dogs can also be affected if they inherit the mutated gene from one or both parents.
Testing for PRA
Genetic tests are available for some forms of PRA. These tests can identify dogs that carry the mutated gene, even if they don't yet show signs of the disease. This information is valuable for breeders to avoid producing affected puppies. Also, an eye exam by a veterinary ophthalmologist can detect PRA early.
In conclusion, PRA is a collection of inherited retinal diseases resulting in blindness in dogs, caused by mutations in various genes that affect the proper function of the retina. Knowing the at-risk breeds and having genetic testing available is essential for prevention and management of this disease.
