Progressive Retinal Atrophy (Dominant) - PRA-D
OverviewPRA is a progressive disorder of the retina (the innermost layer of the eye), which is sensitive to light, that eventually leads to blindness in dogs. PRA is essentially the slow death of retinal tissue; the tissue thins considerably over time causing degeneration of the photosensitive rods and cones of the eye. Dominant PRA has various levels of severity of retinal thinning, with the most affected area being the central retina. This condition has been detected in mastiffs as young as 4 months.
Severity - 5
Dominant PRA has a high degree of severity, due to the dominant mode of inheritance; there is a very high risk of affected pups.
PRA does not always have noticeable symptoms until it is relatively advanced. A shine may be apparent in the dog’s eyes, this occurs because the pupils are dilated in an attempt to let in more light and appear dark and glossy, the pupil will also not respond normally to light. Disorientation is a common symptom of PRA, particularly at night. Night blindness generally appears early in the development of the disease as the rods of the eye are affected first, making it difficult for the affected dog to have clear vision in dim light.
Night blindness in most cases will progress slowly to day blindness as the cones in the eye that respond to bright light progressively deteriorate, leading to total blindness. Sadly, like humans, there is no treatment or cure for blindness in dogs.
Animal Network provides a DNA test that determines the genetic predisposition to dominant PRA .
Progressive Retinal Atrophy (dominant PRA) is an autosomal dominant disease. There are no carriers of a dominant phenotype (trait or disease), and only a single copy of the phenotype causing gene variant is required for the phenotype to be expressed. A direct gene test can detect whether a dog is clear or affected by the disease.
When either parent has two copies of a dominant gene variant they will produce affected offspring 100% of the time. If both parents have only a single copy of the disease, they will produce affected offspring 75% of the time. In the case of only one parent holding a single copy of the dominant gene variant, 50% of their offspring will be affected, a clear dog mated with an affected dog has only a 25% chance of producing clear offspring. Due to the mode of inheritance, there is a higher risk of a dog being affected by dominant PRA. Taking into account the serious nature of the disease, it is advised that affected dogs are excluded from breeding programs.
For an explanation of possible genetic status of offspring please refer to our fact sheet on Breeding strategies. ORDER A TEST