Progressive retinal atrophy

Progressive Retinal Atrophy (PRA) is a group of genetic diseases seen in certain breeds of dogs and, more rarely, cats. It is characterized by the bilateral degeneration of the retina, causing progressive vision loss culminating in blindness. The condition is not painful, and affected animals adapt well to their slowly diminishing sight, provided their environment remains constant.

Causes and Genetics

PRA is primarily caused by mutations in multiple genes that are crucial for the normal functioning of the photoreceptors in the retina. These mutations lead to the degeneration of the rods and cones, which are the light-sensitive cells responsible for vision. The disease is inherited in an autosomal recessive manner in most breeds, meaning that a dog must inherit two copies of the mutated gene (one from each parent) to show symptoms. However, some breeds show an autosomal dominant pattern of inheritance.

Symptoms

The first sign of PRA is usually night blindness. Affected animals have difficulty seeing in low light conditions. As the disease progresses, their vision during the day also deteriorates. This can be observed as an increased clumsiness, hesitation in unfamiliar environments, or difficulty locating objects. The condition is not painful, and because the loss of vision is gradual, many animals adapt well to their limitations.

Diagnosis

Diagnosis of PRA is primarily based on clinical signs and the characteristic appearance of the retina on ophthalmoscopic examination. Genetic testing is also available for some breeds, which can identify carriers of the disease or those at risk before clinical signs appear. This is particularly useful for breeders.

Treatment and Management

There is no cure for PRA, and treatment options are limited. Management of the condition focuses on helping the affected animal adapt to its diminishing vision. This includes keeping the environment consistent, avoiding rearranging furniture, and using verbal cues or scents to help the animal navigate its surroundings. Antioxidant supplements have been suggested to slow the progression of the disease, but evidence of their effectiveness is anecdotal.

Breeding and Prevention

The most effective way to prevent PRA is through responsible breeding practices. Genetic testing of breeding animals allows breeders to identify carriers and affected individuals, thereby preventing the disease from being passed on to offspring. Breeding strategies can include mating carriers with non-carriers to avoid producing affected puppies while maintaining genetic diversity within the breed.

In Other Animals

Though most commonly seen in dogs, PRA also occurs in cats, particularly in certain purebred lines. The condition is similar in nature and progression to that seen in dogs. Template:Veterinary-stub