Health Issues
 

PRA

Progressive retinal atrophy (PRA) refers to a group of diseases affecting the retina at the back of the eye. These diseases cause the cells of the retina, which initially look and function normally, to become increasingly abnormal over time. In most cases, given a long life, the eventual outcome is blindness. Some form of PRA has been recognized in over 100 canine purebreds, and at present there are 7 different genetic types of PRA described.

PRA is inherited, meaning the disease genes that cause PRA are passed from generation to generation. In Toy and Miniature Poodles one specific type of recessively inherited PRA predominates, although there are clues indicating at least one more type is present at a low frequency in the breed. This predominant form of PRA in Toys and Miniatures is the progressive rod-cone degeneration (prcd) form of PRA. Rod cells in the retina slowly lose normal function, resulting in diminished vision in dim light situations and diminished field of vision. Subsequently, cone cells in the retina lose normal function, resulting in diminished vision in daylight situations and eventual total blindness. The age of onset and the rate of disease progression are variable among different breeds, within the same breed and within the same litter. In general for Toys and Miniatures, diagnosis of prcd-PRA made around 3 years of age, based on an eye exam by a veterinary ophthalmologist. Some prcd-PRA affected dogs retain some useful vision throughout their life, while others progress to blindness in mid-life. Unfortunately there is no treatment or cure for PRA.

A genetic test, offered by OptiGen, is used to identify Toys and Miniatures as Pattern A – normal, Pattern B – probably carrier, and Pattern C – probably affected. Within the first 1000 Toys and Miniatures tested by OptiGen, 3-4% are Pattern C and 25-30% are Pattern B. Use of this test for breeding programs is discussed at OptiGen’s website. Identification of breeding animals affected with prcd-PRA or carriers of prcd-PRA is essential to avoid producing affected offspring. This genetic test is not offered for Standard Poodles, since prcd-PRA is not yet a proven cause of blindness in Standards.

Not all retinal disease is PRA and not all PRA is the form currently detectable in your breed. Accurate diagnosis is essential. A dog can test as normal or carrier, yet be affected by a different type of PRA. Although more than one type of retinal degeneration probably occurs in every breed, by far the most common type of PRA for Toys and Miniatures is prcd-PRA.

Yearly eye examinations for general eye health should be done on breeding dogs by a veterinary ophthalmologist, even after testing by OptiGen. The Canine Eye Registration Foundation (CERF) maintains a registry. Click here to learn more about PRA in Poodles and the great strides that are being made in DNA testing.