Seeing a Brighter Future: Genetic testing for progressive retinal atrophy has allowed greater flexibility in breeding.
D. Caroline Coile, Ph.D.
The lights from the instrument flickered in the puppy’s eye. I looked at the screen that would tell the ophthalmologist if its retina was responding. The news was bad: the puppy was another in this litter that was going to be blind.
This was 20 years ago, when the only way to determine if a dog was a carrier of progressive retinal atrophy was to breed it to a dog with PRA and see if any puppies were affected. That day held a sad result for the breeder, whose stud would now be neutered. It was even sadder for the test puppies. They would be completely blind by 2 years of age.
With PRA, the two types of retinal receptor cells (rods and cones) responsible for vision function normally in early life, but later degenerate and die. The rods, which are responsible for vision in low light, die first, so affected dogs initially have difficulty seeing in dim light. The cones, which are more important for detail, movement and color vision, eventually deteriorate as well. The dog gradually loses its vision even in bright light, until it is completely blind. The age at which this happens varies among breeds.
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