Progressive retinal atrophy (PRA) is a hereditary disease that affects a dog's ability to see. There are two different forms of PRA that progress towards blindness. While not painful, PRA is life-changing for a dog—and its owner. Understanding this condition can help you prepare for the challenges of caring for a visually challenged or sightless dog.
What Is Progressive Retinal Atrophy?
Progressive retinal atrophy is the degeneration of the retina (the rear layer of the eye). It primarily affects the cells of the retina called rods and cones, which pick up light, movement, and color. It can also degrade the pigmented epithelium layer that helps protect the rods and cones. Eventually, the degradation of these ocular surfaces leads to blindness.
Symptoms of Progressive Retinal Atrophy in Dogs
The most obvious signs of progressive retinal atrophy are directly related to a dog's ability to see well. It can take months or years for the disease to fully impair a dog's eyesight. If you observe the following signs, call your vet to schedule an eye exam.
Dogs can normally see well in dark conditions, but a dog with progressive retinal atrophy will have trouble seeing in dim lighting or at night. Getting lost in the dark or showing reluctance to enter dark spaces are signs that a dog may be experiencing vision problems. Night blindness occurs first in dogs with progressive retinal atrophy. As the rods further degenerate, daytime blindness will ensue.
As a dog's vision fades, it may bump into unfamiliar objects. A dog may be able to navigate surprisingly well around well-known furniture and walls in its home, but new objects or obstacles in unfamiliar environments can cause collisions.
A dog that begins ignoring common hand signals or visual commands should be observed for the other signs of PRA. What may, at first, seem to be a sudden bout of stubbornness may be a loss of vision.
Causes of Progressive Retinal Atrophy
The exact cause of PRA is not fully understood, but veterinary researchers have determined that it is an inherited autosomal recessive disorder, meaning that an affected dog inherited the defective gene from both parents.
Both purebred and mixed breed dogs can be afflicted with progressive retinal atrophy, but it is most commonly seen in the following breeds:
- Miniature and toy poodles
- Cocker spaniels
- Labrador retrievers
- Tibetan terriers
- Miniature long-haired dachshunds
- Yorkshire terriers
Diagnosing Progressive Retinal Atrophy in Dogs
If your dog experiences vision loss, your vet will perform a thorough eye exam and tests to help identify the problem. In some ways, it is a process of elimination. Because PRA is a progressive condition that can take years to impair vision, other acute eye disorders will be considered and ruled out. An electroretinography test may be performed to measure the electrical responses of your dog's eyes and help determine if progressive damage is occurring in the retina.
Your vet will probably refer you to a veterinary ophthalmologist due to the complexity of most eye issues, including PRA, in dogs.
There is currently no effective treatment for progressive retinal atrophy in dogs. If cataracts have developed as an associated complication of PRA, it is typically not recommended to surgically remove them because the procedure is invasive and will not improve the dog's sight.
Further research into gene therapy may offer dogs with PRA a cure by introducing a normal copy of the CNGB1 gene (the gene associated with the disease), but this is not presently a widely available therapy or cure.
Prognosis for Dogs With Progressive Retinal Atrophy
Eventually, a dog with PRA will go blind. This is not a painful disease, so helping a pet navigate its environment as it loses its vision is your best course of action if gene therapy is not an option. The layout of furniture should not change in a blind dog's home, and extra care should be taken when walking a blind dog outdoors (or in a new environment) to ensure it does not run into objects. You may also want to get your dog a supportive aid called a halo for further protection in its environment.
How to Prevent Progressive Retinal Atrophy
Since PRA is a hereditary disease with no other known cause, selective breeding is the only measure that can be taken to help reduce its prevalence in the population. A DNA test may be available at some veterinary hospitals to help identify if your dog is a carrier of the disease.
Types of Progressive Retinal Atrophy in Dogs
Two main forms of progressive retinal atrophy affect dogs and they are both considered to be hereditary:
- Generalized progressive retinal atrophy (GPRA): The most common form of PRA, generalized progressive retinal atrophy, can occur in both young and old dogs. In early-onset GPRA, the rods and cones have not properly developed, so the dog has vision problems. In late-onset GPRA, the vision loss is gradual since the rod and cone cells deteriorate over time. This form of PRA isn't usually noticed until at least three years of age when a dog starts exhibiting signs of vision impairment.
- Central progressive retinal atrophy (CPRA): The less common form of PRA, central progressive retinal atrophy is also known as retinal pigment epithelial dystrophy (RPED). This rare type of eye disease causes the pigmented layer of the retina to deteriorate and therefore makes it difficult for a dog to see in low light. It is most often seen in older dogs and does not always cause complete blindness.
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Progressive Rential Atrophy in Dogs. VCA Animal Hospitals.
Progressive Retinal Atrophy (PRA) Fact Sheet. Davies Veterinary Specialists.
Disorders of the retina, choroid, and optic disk (Ocular fundus) in dogs. Merck Veterinary Manual.
Person. “Gene Therapy That Restores Vision in Dogs May Help Humans, Too.” MSUToday, Michigan State Univeristy, 18 May 2018.