Collie eye anomaly (CEA), a genetic disease which causes improper development of the eye and possible blindness, is a common ailment in the breed. More rarely, Rough Collies can be affected by progressive retinal atrophy (PRA), another genetic disease in which bilateral degeneration of the retina results in progressive vision loss culminating in blindness. Through genetic testing and careful screening program it would be theoretically possible to eradicate both of these problems in purebred lines, however, certainly in the UK, the Kennel Club does not require these tests to be done either for registration or showing. CEA is so prevalent that elimination of affected dogs except through very slow and careful breeding decisions to avoid shrinking the gene pool more than absolutely necessary. Rough Collie puppies should be screened at an early age (6–8 weeks) by a certified veterinary ophthalmologist to check for CEA. PRA has a later onset and can be detected by DNA test, but is much less widespread (in the US) than CEA. (In the UK, PRA is more common. ) Note, the UK Kennel Club "Accredited Breeder Scheme" requires eye tests and recommends the genetic test for this class of members.