Progressive Retinal Atrophy, crd1 in dogs: Canine genetic health condition information

What is PRA-crd1?

This retinal disease causes progressive, non-painful vision loss. The retina contains the cells, photoreceptors, that collect information about light: that is, they are the very beginning of how we see. There are two types of photoreceptors: rods, which gather information about light intensity and are the major contributors to night vision, and cones, which distinguish color and are the major contributors to day vision. In nearly all forms of PRA, the rod cells are affected first, leading to night blindness. They are followed by the cone cells, leading to day blindness. The mechanisms by which the photoreceptors degenerate vary depending on the specific mutation that causes PRA. However, the readout is the same: the dog experiences a slow loss of vision, often leading to complete blindness. PRA is a subtle disease: most owners do not even know that their dog has gone blind--you may notice that your dog is reluctant to go down the stairs, or bumping into door frames or corners, or taking a very long time to fetch a ball or toy. A peek at your dog’s eyes in bright light may also reveal a sluggish pupillary constriction, because the retina is no longer telling your pupils that it is letting in too much light; however, definitive diagnosis of PRA requires a trip to the vet. Because of the slow progression of PRA, most dogs adapt very well to their condition. Over time, affected dogs can develop cataracts, thought to be due to buildup of reactive oxygen species and other toxic metabolites released from the degenerating retinal cells. This can lead to other complications and requires close monitoring in consultation with your vet.

What are the signs & symptoms that develop in affected dogs?

PRA is a subtle disease and dogs adapt very well to the slow loss of vision. You may notice that your dog is reluctant to go down the stairs, bumps into door frames or corners, or takes a longer time to fetch a toy.

When do signs and symptoms develop?

An ophthalmologist can first see signs of this disease by 6 months of age, with complete blindness typically occurring by 2 years.

How do vets diagnose this condition?

Veterinarians use a focused light to examine the pupils. In affected dogs, the pupils will appear more dilated and slower to contract. Your vet may also use a lens to visualize the retina at the back of the eye to look for changes in the optic nerve or blood vessels. You may be referred to a veterinary ophthalmologist for a definitive diagnosis.

How is this condition treated?

Currently, there is no definitive treatment for PRA. Supplements, including antioxidants, have been proposed for management of the disease, but have not been scientifically proven effective.

Progressive Retinal Atrophy, crd1