Genetic Eye Diseases in Golden Retrievers
Genetic eye diseases in Golden Retrievers fall into two categories, those that should be tested for on a yearly basis by a board certified veterinary ophthalmologist and those that can be tested for by a DNA test.
The clearance that is given after a dog is examined by an ophthalmologist is called a CERF clearance. CERF is a company that was founded with a goal of “eliminating heritable eye disease in all purebred dogs by forming a centralized, national registry”. In order for a dog to get a CERF clearance, he/she must be examined by a veterinary ophthalmologist who will screen for a wide variety of genetic eye problems. See CERF’s link http://www.vmdb.org/categories.html which gives the list of conditions that the ophthalmologist is required to screen for. In order to be screened for CERF, a dog must be clear of all the eye conditions on this list and the ophthalmologist must send the report to CERF. A CERF certification is only valid for a year because genetic eye conditions can develop at any age. Therefore, CERF, OFA, and the Golden Retriever Club of America all suggest that breeders have their breeding dogs reevaluated every year so that if an inheritable eye disease develops, the breeder knows it and can remove the dog from his/her breeding program.
Once a month, CERF sends a list of dogs who were recently cleared for their CERF certification to OFA and OFA updates their database with that information. OFA’s primary function is to evaluate hip and elbow dysplasia and making these results available to the public, but they also provide a place for breeders to report to the public eye and cardiac clearances. With CERF making their database available to OFA, it makes it easier to research most all of the health clearances of a dog in one place.
In recent years, genetic tests were made available to the public for a group of diseases called PRA that causes retinal atrophy. Atrophy of the retina does not normally show up until after a dog is old enough to have been bred. This condition starts off with limited night vision and then progresses to eventual blindness. These DNA tests will enable a breeder to identify dogs that have this gene before the dog is bred, before the dog ever develops symptoms, or even before an ophthalmologist is able to see evidence of it. This test will also enable breeders to identify dogs who are carriers of the disease. With this information, breeders can make sure that when they plan breedings, all dogs who are either carriers of or are genetically predisposed to be affected by PRA will be bred only to dogs that are clear. Because the PRA gene is a recessive gene, one clear parent guarantees that none of the puppies will be affected.
Not all types of PRA are identifiable with a DNA test, but two of the most common types are: Prcd-PRA and GR_PRA1. One type is found in North American lines. The other is found in European lines.
Prcd-PRA is a form of PRA that is found only in American and Canadian lines of Golden Retrievers. According to Optigen, the testing organization, all of the Golden Retrievers tested as “affected” with this type of PRA are from North America lines. The DNA test for Prcd-PRA became available for use in 2008 and although only about 1% of those Golden Retrievers tested have test results of “affected”, about 25% are carriers of it. If two carriers are bred together, roughly ¼ of the offspring will be “affected” by it. With this high percentage of carriers, it is important that this test is done in American Goldens.
The test for GR_PRA1 was not devised until 2010. GR_PRA1 is the most prevalent type of PRA in European lines with about 5% being affected by it. Only .5% of American Golden Retrievers are affected by this type of PRA. This is the type PRA that we test for at Summer Brook.
There is a registry for dogs who have had DNA tests at www.goldendna.com. The results from the testing companies are not automatically sent to this registry. Breeders must fill out the paperwork and send copies of the results to the registry themselves.
The number of Golden Retrievers affected with genetic eye diseases can greatly be reduced if all breeding dogs were screened with the appropriate DNA test for PRA and if breeders would annually have their dogs screened for other genetic eye diseases through CERF. Some affected dogs might go undetected because of a genetic disease not showing up until the dog is past breeding years. However, with good communication between breeders, the offspring of these dogs could be retired before they possibly contribute defective eye genes to the gene pool.
See the following links for further reading on genetic eye diseases.