Genetic Blindness in Dogs
By Deborah Boudreau Progressive Retinal Atrophy - PRA - is a genetic, inherited disease present at birth and results in blindness as the dog matures. PRA slowly adds a film over the lens of the eye similar to cataracts. This film restricts and eventually stops the flow of light into the eye.
There are two tpes of PRA. early onset and late onset. The only difference is the point in time where the disease surfaces.
In early onset PRA, the condition surfaces rapidly, and can be seen in puppies as soon as their eyes open. These pups have trouble seeing in dim light and darkness. Often the owner thinks the pup is just uncoordinated or still in developmental stage and don't realize ir is really poor eyesight. As the pup gets older the eyesight gets worse and are completely blind by the time they are 5.
Late onset PRA is not apparent until after the first year. Occasionally the dog is well past 5 years of age before it shows itself. As with early onset, the first sign is night blindness, With indoor dogs, it is harder to notice the diminishing eyesight because the house is lit in the evenings.
PRA is a recessive gene that is found in all dog breeds. It can be found in any size, breed, gender, including the good old fashioned mutts. As long as both parents carry the gene. However there are breeds where it is more prominent.
In the Samoyed and the Siberian Husky, PRA is only found in males.. In the Old English Mastiff and the Bullmastiff, however, PRA is the dominant gene. Testing is ongoing to determine the genetic placement in other breeds.
PRA does not cause discomfort nor is it the cause of any other neurological or heath issues. Most dogs adapt to their lack of vision, and live happy, normal lives. Fenced yards and never leaving the house without a leash is very important. Also, rearranging furniture or moving to a new home will cause the dog to become disoriented until he becomes used to the new layout.
Ongoing research is being done, not only to determine where in the genetic makeup the gene lies in various breeds, but into possible treatments as well. So far, research indicates that foods high in antioxidants may slow down the vision loss. Unfortunately, it cannot stop or reverse any damage that has already been done. Genetic testing for this disease before breeding may help to eliminate it from breeding lines where it is commonly found.
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