What is PRA?
Progressive retinal atrophy is the name of a group of hereditary diseases that involve degeneration of the retina and eventual blindness. The disease is inherited and occurs in both eyes (bilateral). There are many different forms of PRA, and each of the forms are the result of a specific hereditary defect. Purebred dogs are most commonly affected, and specific breeds are predisposed to specific types of PRA. At this time, there is no treatment for PRA.
Despite the form of PRA, most dogs present with similar clinical signs. The age of onset will vary between breeds. Diagnosis of PRA by your veterinarian can be made with an eye exam and an electro-retinogram (ERG), which detects activity of the retina. Diagnosis can be assisted with genetic testing.
Clinical Signs of PRA
- Impaired night vision (nyctalopia)
- Dilated, non-responsive pupils
- Increased tapetal reflection, or “eye shine”
- Cataracts (late in the disease)
- Eventual blindness
Prcd-PRA (Progressive rod-cone degeneration)
This form of PRA is the most common. The symptoms first appear as night blindness then progress to loss of sight in daylight and eventual total blindness. It is caused by a recessive genetic trait, requiring that both parents pass on a mutant, disease-causing gene. Parents can either be carriers (1 mutant gene, 1 normal gene) or affected animals (2 mutant genes). Prcd-PRA can be prevented through strategic breeding of tested dogs. There is a genetic test available for this form of PRA for many breeds. More information can be found at
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Dominant PRA of Mastiffs & Bullmastiffs
Mastiffs and bullmastiffs are the only breeds known to be affected with a dominantly-inherited form of PRA. This means that only one copy of the mutant gene is required to cause the disease. Genetic testing can identify a dog as normal, heterozygous affected (1 mutant gene, 1 normal gene), or homozygous affected (2 mutant genes). About 50% of the puppies of a heterozygous animal will be affected, and 100% of the puppies of a homozygous animals will be affected.
Other Forms of PRA
Welsh corgis are affected by a form of PRA called rcd3-PRA (rod & cone degeneration type 3). Irish setters can be affected by rcd1-PRA. The mutation in miniature schnauzers is called Type A-PRA, because there are multiple causes in this breed. In Samoyeds and Siberian huskies, the disease is X-linked (on the X chromosome). This form is called XL-PRA.
For more information on this subject, speak to the veterinarian who is treating your pet.