Genetic disorders are prevalent in many canine populations because of the reduced heterogeneity of purebred dog breeds. OptiGen is a veterinary diagnostic company specializing in canine inherited eye diseases that has been providing DNA testing services to purebred dog breeders since 1998. During this period, many individuals representing more than 60 pure breeds of dog have been tested at OptiGen for mutations causing a variety of retinal diseases. OptiGen's twelve-year collection of genotypes, together with the detailed pedigree information and eye-health records of the tested dogs, has allowed the construction of an extensive database that provides valuable insights into the scale of specific inherited disorders in the purebred dogs. For some diseases (e.g., progressive rod cone degeneration, collie eye anomaly) the identical mutation has been observed to segregate in multiple breeds. In other diseases (e.g., canine multifocal retinopathy, canine achromatopsia [cone degeneration]), allelic mutations are observed in different breeds. Many other diseases however appear to remain breed-specific (e.g., rcd2, CSNB, and crd3). We have also identified multiple cases where a clinical disease that closely resembles that caused by a known specific mutation, turns out by DNA testing to be a phenocopy - having a wild type/normal genotype for the mutation. These findings and trends in disease incidence and carrier frequency over the last twelve years will be described and discussed.