Do you suspect your dog is having vision trouble? Maybe they seem nervous in dimly lit spaces, hesitate in unfamiliar environments, or bump into objects more often than before.
One possible explanation is progressive retinal atrophy (PRA), an inherited eye disease that causes the retina’s light-sensing cells to gradually deteriorate. Over time, PRA leads to vision loss and eventual blindness, although affected dogs can often continue to enjoy a high quality of life with proper support.
What Is Progressive Retinal Atrophy?
According to Dr. Jerry Klein, Chief Veterinarian for the American Kennel Club, “Progressive retinal atrophy is, as the name implies, a gradual progressive degeneration of the photoreceptor cells in the retina, causing gradual vision loss, eventually leading to blindness.”
To fully understand PRA, it helps to know how the retina works. The retina is the light-sensitive layer at the back of the eye. It contains specialized cells called photoreceptors that detect light. These cells send signals through the optic nerve to the brain, which forms and interprets the images.
There are two main types of photoreceptors:
- Rods, which function best in low-light conditions and help detect motion
- Cones, which are responsible for color vision and require brighter light
PRA affects both rods and cones, causing vision to decline over time.
It’s important to note that PRA isn’t the only cause of slowly developing blindness in dogs. Dr. Klein notes that several other conditions can produce similar symptoms:
Because these conditions can look alike from the outside, an accurate diagnosis is essential.
Dr. Klein explains: “Diagnosis of PRA requires a thorough retinal exam performed by a veterinarian who will often refer to a board-certified veterinary ophthalmologist. On some occasions, further diagnostics need to be performed to measure the electrical activity of the retina and evaluate possible development of other ocular conditions such as cataracts.”
When Does PRA Develop in Dogs?
The progression of PRA is usually slow, with complete loss of vision often occurring over one to two years. However, the rate of progression can vary depending on the dog’s breed and the specific form of the disease.
PRA can affect dogs at different ages. Dr. Klein says, “There are two basic types of PRA recognized in dogs. Early onset, also called retinal dysplasia, is usually found in young puppies around 2 to 4 months of age. Most PRA is seen in adult dogs from 3 to 9 years of age.”
Early-onset PRA occurs when retinal cells fail to develop normally. The more common late-onset form develops after the retina has matured and begins to degenerate later in life.
Signs and Symptoms of PRA
Because vision loss develops gradually, owners may not notice PRA during its earliest stages. The condition isn’t painful, so dogs often continue behaving normally while their vision slowly declines.
Dr. Klein explains: “Since PRA is not a painful condition, many owners may not notice early onset. At some point, most owners notice hesitancy when their dogs move or walk in dark areas or different surroundings. Some dogs may become more anxious in dark or shaded areas.”
Common signs of PRA include:
- Difficulty seeing in dim light or at night
- Hesitation in unfamiliar environments
- Increased anxiety in dark or shaded areas
- Dilated pupils
- Increased eye shine or stronger light reflection from the eyes
- Gradual loss of daytime vision as the disease progresses
If you notice any of these signs, schedule a veterinary examination to determine the underlying cause.
What Causes Progressive Retinal Atrophy?
The underlying cause of PRA is the degeneration of the retina’s photoreceptor cells.
As described above, this can happen because the cells never developed normally (early-onset) or because they developed properly but broke down later in life (late-onset).
Dr. Klein explains, “Typically, the rod cells start to atrophy first, causing night blindness, and then the cone cells atrophy, leading to complete blindness.”
This pattern explains why many dogs initially struggle in low-light conditions before losing vision during the day as well.
What Does It Mean if a Dog Is a PRA Carrier?
PRA is an inherited disease caused by genetic mutations that affect retinal development or function.
In some breeds, such as Mastiffs and Bullmastiffs, PRA appears to be inherited as a dominant trait, meaning a dog may develop the disease after inheriting just one copy of the affected gene. In other breeds, such as Samoyeds and Siberian Huskies, inheritance can be linked to the dog’s sex and occurs primarily in males.
Most cases of PRA, however, follow an autosomal recessive inheritance pattern. This means a dog must inherit a defective gene from both parents to develop the disease.
Dogs that carry only one copy of the affected gene are known as carriers. These dogs typically don’t develop PRA but can pass the gene to their offspring.
As Dr. Klein says, “Carriers may not have any signs of impaired vision but carry the gene, and when crossed with another carrier, they can produce affected individuals, other carriers, and possibly unaffected dogs.”
Dog Breeds Commonly Affected by PRA
PRA can occur in both mixed-breed and purebred dogs. Some breeds that are commonly affected include:
- Miniature Poodle
- Toy Poodle
- Cocker Spaniel
- Yorkshire Terrier
- Tibetan Spaniel
- Labrador Retriever
- Miniature long-haired Dachshund
- Bedlington Terrier
Because PRA is inherited, responsible breeding practices and genetic testing can help reduce the risk of passing the disease to future generations.
Caring for a Dog With Progressive Retinal Atrophy
There is currently no effective treatment that can stop or reverse PRA. Management focuses on helping dogs adapt safely to vision loss while maintaining their quality of life.
Many dogs adjust remarkably well because they rely heavily on other senses, especially smell and hearing. Consistency is often one of the most helpful ways to support a visually impaired dog.
Dr. Klein suggests, “Trying to keep environmental consistency of a vision impaired dog is paramount for their safety and security. For the average family dog, blindness does not seem to be as significant an issue as it is in a person. Dogs rely heavily on other senses, such as smell and sound, and are able to move around fairly well in their home as long as furniture and other objects are not moved around.”
Dogs with PRA can still enjoy daily walks, enrichment activities, training, and even participating in certain dog sports.
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