Progressive Retinal Atrophy Type III

Progressive Retinal Atrophy (PRA) is a disorder that causes the degeneration of the light sensing retina at the back of the eye, resulting in vision loss.

Key Signs

Degeneration of the photoreceptor cells of the retina, Night blindness, Vision loss, Blindness

Age of Onset

1 to 4 yrs

Junior to adult onset


Autosomal Recessive

For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.

Likelihood of the Condition

High likelihood

At risk dogs are highly likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a dog with PRA type III

Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about PRA type III

The onset of clinical signs of PRA type III is typically at 5 years of age with initial loss of vision in dim light (night blindness) which gradually progresses to total blindness. The first signs are caused by loss of rod photoreceptor cells required for vision in dim light followed by reduction of the visual field and blindness as the cone cells of the retina also degenerate.

A blind dog tends to adapt well to the loss of vision. However, some dogs may exhibit a tentativeness when introduced to unknown environments because their vision is compromised. Occasionally, they may react abruptly (snapping) if they are startled so caution and use of verbal queues should be taken when handling a blind dog. Caretakers should take precautions to protect the blind dog from threats it cannot detect (ex. cliffs, sharp points on furniture, moving vehicles).

For Breeders

Planning to breed a dog with this genetic variant?

There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to occur. A carrier dog with one copy of the PRA type III mutation can be safely bred with a clear dog with no copies of the PRA type III mutation. About half of the puppies will have one copy (carriers) and half will have no copies of the PRA type III mutation. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. Please note: It is possible that disease signs similar to the ones caused by the PRA type III mutation could develop due to a different genetic or clinical cause.

Technical Details

Gene FAM161A
Variant Insertion
Chromosome 10
Coordinate Start 61,822,372
Coordinate End 61,822,373

All coordinates reference CanFam3.1

References & Credit

Credit to our scientific colleagues:

Downs, L. M., & Mellersh, C. S. (2014). An intronic SINE insertion in FAM161A that causes exon-skipping is associated with progressive retinal atrophy in Tibetan Spaniels and Tibetan Terriers. PLoS ONE, 9(4), 1–12. View the article