Progressive retinal atrophy in dogs: Symptoms, treatment and breeds at risk

What is progressive retinal atrophy in dogs?

Progressive retinal atrophy (or PRA) is a non-painful genetic eye condition that affects the retina in a dog’s eyes and eventually causes blindness. Vision loss takes place gradually, but most dogs experience total blindness within two years of the onset of the disease.  

Similar to retinitis pigmentosa in humans, there is no cure for PRA, but genetic testing can be done to detect the condition. Some breeds are more susceptible to the condition than others, including miniature long-haired dachshunds, English springer spaniels, golden retrievers and American cocker spaniels.

How does PRA affect dogs?

PRA damages the two types of light-sensitive photoreceptor cells in the retina: the cones and rods. Cone cells detect color and provide daytime vision, while rod cells help a dog see in low light.

Dogs have more rods than they do cones — and the rods are usually affected first in cases of PRA. Since the rods are responsible for seeing in dim light, one of the first signs of PRA in dogs is the progressive loss of night vision. 

The cone cells are slower to deteriorate, but once they do, the dog will experience blindness in both night and day settings.

“Atrophy” is a word used to describe a specific body part that wastes away or deteriorates. “Progressive” refers to something that takes place over time, and “retinal” means it has to do with the retina. So when you put it all together, “progressive retinal atrophy” translates to the wasting away of the retina over time. 

PRA is mainly seen in purebred dogs, but mixed breeds can have the condition as well. 

Causes

PRA is an inherited condition caused by a genetic mutation, so if a parent dog carries the mutation, they can pass it on to their offspring. 

For the majority of dogs, the genetic mutation in question is usually recessive, meaning both parents must carry it for the condition to be inherited by their offspring. But some dogs, such as bullmastiffs and English mastiffs, can inherit PRA from a dominant gene so only one parent needs to be a carrier. 

In breeds such as the Siberian husky and the Samoyed, PRA is thought to be a sex-linked trait and is found mostly in males. 

PRA can occur early in life if the cells in the retina develop abnormally. It can also develop in adulthood if the retinal cells begin to degenerate.

In some cases, a form of PRA called sudden acquired retinal degeneration (SARD) can also occur. SARD is acquired (not genetic) and the cause is unknown. 

Breeds at higher risk of developing progressive retinal atrophy

Several breeds are associated with PRA. This includes breeds such as:

• American cocker spaniels

• Bedlington terriers

• Bullmastiffs

• Cavalier King Charles spaniels

• English springer spaniels

• Miniature dachshunds

• Golden retrievers

• Labrador retrievers

• English mastiffs

• Rottweilers

• Samoyeds

• Siberian huskies

In Samoyeds and Siberian huskies, PRA is more often found in males. Regardless of the breed, genetic testing can be performed to detect PRA if your dog may be at risk.

Types of PRA

The two main types of PRA found in dogs are split up by age group:

• Early-onset PRA (also called retinal dysplasia) is diagnosed in puppies, often between 2 and 3 months old. In this type of PRA, the cone and rod photoreceptor cells do not develop properly, which causes blindness to set in early.   

• Late-onset PRA is diagnosed in older dogs, usually between the ages of 3 and 9 years old. With late-onset PRA, the photoreceptor cells develop properly but waste away over time. One of the most common forms of late-onset PRA is progressive rod-cone degeneration (PRA-prcd).

Both early- and late-onset PRA end in total blindness for the dog. 

A third acquired type of PRA can affect dogs too. Sudden acquired retinal degeneration (SARD) causes sudden blindness over a period of days or weeks. SARD is not inherited and occurs later in life than both early- and late-onset PRA. The cause of SARD is unknown.

Symptoms 

Since PRA causes gradual vision loss, many of the early signs associated with the disease reflect how your dog adjusts to losing their sight. Some behaviors you may notice include:

• Hesitancy to enter a dark room

• Nervousness at nighttime

• Clumsiness in dim light or in unfamiliar surroundings*

*”Unfamiliar surroundings” are not just restricted to new environments. If you’ve recently rearranged the furniture in your home, make sure your dog still has clear paths they can navigate. 

Some physical symptoms of progressive retinal atrophy in dogs, which occurs in both eyes, may include:

• Noticeably dilated pupils, even in bright light

• Eyes that appear very reflective when a light shines on them

• Blindness

Unlike some other eye problems in dogs, PRA is not a painful condition, so your dog likely won’t show signs of discomfort. If you notice any of the symptoms above or have any other concerns about your dog’s health, contact your veterinarian. 

Genetic testing

To date, more than 20 PRA-causing gene mutations have been identified in over 100 dog breeds. A number of commercially available dog DNA kits test for PRA variants to help breeders and owners understand their dog’s risk for developing (and passing on) the disease. Results for each test will come back as one of the following:

• Normal (or clear) – This means your dog does not have any copies of the genetic mutation tested for, and they will not develop PRA due to this mutation. 

• Carrier – This means your dog carries one copy of the mutated gene and one normal copy of the gene — one from each parent. They won’t develop PRA from this mutation, but they will pass a copy of the mutation to around half of their offspring.

• Affected – This means your dog has both copies of the mutated PRA gene and is likely to develop this form of PRA at some point in their life. However, age at onset and severity of symptoms can vary for each dog.

If your dog’s DNA test comes back as genetically affected for PRA, it’s important to have their eyes and vision assessed by your vet, and likely a veterinary ophthalmologist, for a proper diagnosis. You should also monitor their visual ability in different settings.

Diagnosis

To fully diagnose PRA in a dog, the following steps are taken:

1. Your vet will perform a general eye exam first. If the exam reveals dilated pupils that are slow to respond to light, PRA may be present. However, retinal changes at the back of the eye may be hard to detect without more specialized equipment.

2. The back of the eye is then examined using a special instrument called an ophthalmoscope. This exam can tell the vet if there have been any changes in the retinal blood vessels or the optic nerve.

3. To confirm a PRA diagnosis, your vet will refer you to a veterinary ophthalmologist for further testing. They will perform a diagnostic test called an electroretinogram (ERG), which tests how the retina responds to a light stimulus. ERG testing can actually detect PRA before a dog shows signs or symptoms of it.

A veterinary ophthalmologist will also check for any other causes of blindness before confirming that PRA is the condition at hand. 

Treatment

There is no current treatment that can cure progressive retinal atrophy in dogs, or reverse its effects. 

Some claim that vitamins and antioxidant therapy may help treat the disease, but there is no clinical proof of this. However, vitamins and antioxidants may help relieve some of the stress put on the eyes, including inflammation. They may also help delay the development of cataracts.

With the help of their owners, dogs can adapt to a life without sight. Talk to your veterinarian and trainer about how you can help a visually impaired dog find their way around and live their best life.  

How does PRA affect dogs in the long run?

The primary effect of PRA is blindness. 

As PRA progresses, a dog’s risk of developing cataracts may also increase. Vets may not recommend cataract removal surgery if a dog also has PRA since PRA will cause them to go blind eventually anyway. 

Although PRA is not a painful condition itself, it can sometimes cause inflammation in the eyes, which can cause discomfort for your dog. If this is the case, your vet may prescribe anti-inflammatory medication. 

If you believe that your dog may be at risk for PRA or is showing signs of PRA (or any other eye condition), talk to your veterinarian. Testing can be done to detect eye problems and help plan for the future of your furry friend. 

Page published on Wednesday, April 27, 2022

Page updated on Tuesday, April 26, 2022

Medically reviewed on Friday, March 4, 2022