Geneticist Leslie Lyons and ophthalmologist David Maggs are studying Persian cats that have naturally occurring blindness.

Genetically inherited problems with the retina -the tissue layer in the back of the eye that contains the photoreceptor cells (rods and cones) for processing light -can lead to blindness in humans.

Persian cats, the most popular cat breed throughout the world, may also suffer from genetically induced retinal disease and blindness. Persian vision problems start very early, possibly before 4-8 weeks of age, and progress quickly. Cats with inherited retinal disease become completely blind by 16 weeks or easrlier.

The retinal disease in Persians is caused by a mutation in one gene, and two copies of that mutation are required to cause blindness. Carrier cats -cats with one copy of the mutation -are perfectly healthy, but when bred, they can pass the mutation onto their offspring. A genetic test is needed to detect the carriers of the mutation.

Drs. Lyons and Maggs are attempting to match the clinical signs, microscopic pathology and DNA analysis of retinal disease in Persians to a related disease in humans. If the disease in cats closely mimics the disease in humans, they plan, with the help of human data, to use genetic markers to develope a genetic test that can detect cats that are carriers. A cat model of the disease may also help treat human blindness.

Persians are used as breeding stock for other breeds or often are used to change the facial structures of other breeds. Thus, health problems in Persians can be spread quickly and widely in the cat world if unchecked. Once it is possible to avoid breeding carriers, the disease may be eradicated in Persians.