Progressive retinal atrophy (PRA) is a collective term comprising a group of hereditary degenerative lesions of the retina. A central and a generalized form can be differentiated. The central form (day blindness, hemeralopia) is characterized by accumulations of pigment in the layer of pigmented epithelium of the retina, atrophy of the cones and subsequent atrophy of the rods, eventually terminating in blindness. The generalized form (night blindness, nycteralopia) is marked by dysplasia of the rods and or cones, followed later by atrophy of the rods and cones, or it may be marked solely by atrophy of the rods and cones. Blindness occurs between the first and seventh years of life, varying with the breed and form. Hereditary transmission of the generalized form is recessive. Detection of patients is essential in controlling the disease. The number of carriers can be estimated on the basis of this detection, part of the carriers can be identified and the likelihood of an animal being a carrier can be calculated. The condition may be controlled by test matings to determine the genetic patterns of breeding dogs where progressive retinal atrophy is concerned.