Your best bet is to know what genetic tests are needed for the breed that you are interested in, and to ask the breeder to show you the results of those tests. Links See the links on genetics Top of Page Only fancy show dogs need testing before they are bred. Genetic disease in dogs is devastating. Every year, uncounted families are heartbroken when their beloved pets are crippled from hip dysplasia, go blind from progressive retinal atrophy, are found to be deaf, die of cardiomyopathy, or suffer from many other disorders. By conducting thorough genetic screening programs, responsible breeders can greatly reduce their chances of producing an affected puppy.
Irresponsible breeders can make no such claim.
I haven't ever seen a dog with one. Except in extreme old age, most blind and deaf dogs become that way because of genetic disorders such as PRA and congenital deafness of white animals. This tendency is inherited. The list could be a very long one. Many times, we just don't think of our dogs' problems as genetic when, in fact, they are.