Progressive Retinal Atrophy or PRA is the leading cause of blindness in adult dogs of almost every breed and size. It is a genetic condition from which there is no cure either through surgical procedures or drug therapies. As with any type of genetic disease the only true way to suppress the condition is to immediately spay or neuter any dog, mixed or purebred, that exhibits any sign of PRA. It is linked to a recessive gene that means that both the male and female must have the condition for the puppies to display PRA, but they can pass the genetic component onto their offspring, which then may breed with another recessive dog, resulting in a litter with PRA. There are some deviations to this rule as in Bullmastiffs and Old English Mastiffs the condition is a dominant gene and in breeds such as Samoyeds and Siberian Huskies the gene is sex-linked and is only found in males.
Unfortunately this condition may not be genetically programmed to activate until the dog is older, which means that many dogs that are not properly inspected when younger may be used in breeding programs resulting in several litters being born before the condition is noticeably present and diagnosed. An examination by a board certified veterinary ophthalmologist is the most widely acknowledge way to detect even early signs of the disease and should be considered before buying any puppy. Many reputable breeders, especially in breeds where the condition is present, will provide this certification prior to the sale of the puppy. In some breeds there are also specific blood tests that detect the genetic patterns in DNA that indicate the gene is present or absent in the dog. Not all breeds have been genetically mapped to allow this simple DNA test, but many breeds are currently able to be tested this way. As work on DNA and genetics in dogs continues to advance, researchers hope to increase the number of breeds that can be tested via blood samples, and incorporate this type of testing into ethical breeding standards in clubs and associations.
What is progressive retinal atrophy?
Progressive retinal atrophy is a genetic condition that causes the rods and cones, also known as the photoreceptors in the retinal of the eye to cease functioning. This means that the retina no longer captures the pictures that the eye sees, resulting in decreasing vision. Usually the rods or night vision receptors are affected at first, resulting in the dog's inability to see in the dark or in shadowed areas. As the disease progresses the cones will also be affected which results in decreased daytime vision until full blindness occurs.
The length of time that a dog is first diagnosed with progressive retinal atrophy and the time that he or she becomes fully blind depends on the breed of dog, the age of the dog and the severity of the condition. Some dogs and puppies may become fully blind within six months of the first symptoms while others may have several years of moderate amounts of sight until they become fully blind.
What are the symptoms of progressive retinal atrophy?
Thankfully progressive retinal atrophy is not a painful condition nor does it seem to affect most dogs as profoundly as it does many owners. The first symptom that most owners notice is that the dog just seems to constantly be running into things or tripping over objects in the dark. The dog may not want to go outside at night and may be very hesitant to walk in shaded areas, preferring to stay to areas that are brightly lit.
As the cones become affected the daylight vision will also decrease. The pupils will stay highly dilated and open as the eye tries to pick up as much light as possible. These dogs will often develop a shine or glow to the eye very similar to cataracts, which may develop at a later time as the dog goes blind. This is most commonly noted as a milky or opaque look to the eye even in light.
How is PRA treated?
Unfortunately there are no treatments that can change the course of the degeneration of vision in dogs with progressive retinal atrophy. All dogs with the condition will eventually become totally blind, however this is not necessarily a problem for the dog. Since a dog can use other senses to move around and is able to remember the lay out of rooms and yard areas, a dog with limited or no vision can lead a happy life provided the family provides extra support for the dog and keeps things in the same location as they were when the dog had his or her full vision. Since the loss of vision is gradual the dog really does adjust and, unlike the family, does not feel handicapped or restricted. They will learn to respond more to smell and hearing although for older dogs these senses may also be somewhat limited.
There is new research being completed into using special diets that contain high levels of antioxidants as a way to prolong the vision in dogs with progressive retinal atrophy. While not reversing the condition or preventing the condition from eventually leading to full blindness, some researchers have promising results that can slow down the progression of the disease through antioxidants to give the dog a few more months or even years of limited vision before full blindness sets in.
If your dog has been diagnosed with progressive retinal atrophy start working with him or her about learning their way around the house. Reinforce verbal commands and even obedience work with the dog to help them with support when their vision starts to fade. Consider adding some safety features to the house such as baby gates at the top and bottom of stairways to prevent the dog from moving about in certain areas of the house. Keep the dog on a leash at all times when out of the yard and double check for any safety issues in the house or yard that could pose hazards to the dog.
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