The main objective of this proposal is to continue the study of models of the normal and abnormal visual system. We will use psychophysical and electrophysiological techniques to aid in identifying sites of adaptation and retinal disease. An approach for comparing the psychophysical and electrophysiological data will be developed, and the data will be analyzed within the context of models of the rod and cone systems. These models will be computational models that are explicit in time. They will be used to test hypotheses about sites and mechanisms of disease related sensitivity loss in diabetes and retinitis pigmentosa. We also plan to pursue our interest in S-cone pathway vulnerability. A prospective study will be designed to evaluate whether a measure of S-cone sensitivity can predict the progression of diabetic retinopathy. In addition, using a color monitor, we will develop psychophysical paradigms to test hypotheses about sites and mechanisms of foveal color vision defects found in patients with open-angle glaucoma. The data will be analyzed within the context of recent models of cone systems, models based on recent physiology.