Progressive retinal atrophy in the Abyssinian cat. Clinical characteristics.

Ninety-four cases of a hereditary retinal degeneration in household Abyssinian cats were found in Sweden, mainly during a 3-year period. The disease was investigated by ophthalmoscopy, fluorescein angiography, electroretinography, and light microscopy. A bilateral retinopathy was usually first seen in affected cats at the age of 1.5-2 years. Fluorescein angiography did not demonstrate abnormalities of etiological significance to the disease process. A reduction mainly of a- and b-wave amplitudes in the ERG indicated a generalized photoreceptor disease. Light microscopy showed that the photoreceptor layer was primarily affected, while other retinal layers were mainly normal. The midperipheral and peripheral retina was affected more severely than the retina of the posterior pole until late stages of disease, when there was a generalized loss of photoreceptors. The clinical and laboratory findings suggest that PRA in these Abyssinian cats is a heritable photoreceptor degenerative disease with a fairly slow rate of progression.