The propsed research is designed to characterize the precise pathology of tHe peripheral degeneration of the retina in Fischer rats, and to study the pathogenesis and etiology of this retinal disease. In addition, this research would also provide useful information concerning the aging processes and the interaction between the age-related and light-associated factors in the retinal tissues. This research is divided into three conceptual areas: The first is to characterize the pathology of the disease temporally, spatially and ultrastructurally and to determine the effects of age, sex and light on the disease processes. The second is to study the geometrical distribution and three dimensional characteristics of the retinal lesions in Fischer rats. The third is to determine whether or not the retinal vasculature in affected retinas is involved in pathogenesis of the disease.