Why not just stick with ERGs for finding normal dogs?
Not every ERG exam is done reliably. To establish PRA-affected status by ERG, be sure that a full diagnostic protocol be done with dogs under anesthesia or heavy sedation; the rod and cone contributions of the ERG be separately evaluated. Accurate ERGs cannot be done in 10 minutes, or at a dog show. You need a fully equipped clinic and a trained veterinary ophthalmologist with at least an hour to spare. And: “normal” according to an ERG doesn’t mean “genetic normal.” The dog still could be a carrier. In Labrador Retrievers, Chesapeake Bay Retrievers, Portuguese Water Dogs and Poodles, an ERG to rule out PRA cannot be done before 18 months of age. If a reliable ERG gives “normal” results on a dog that’s 18 months or older, the dog most probably is not affected. In English Cocker Spaniels, Australian Cattle Dogs, Tollers and American Eskimo Dogs, ERG’s have been less reliable.
