Retinal cone photoreceptor outer segments will be studied biochemically to isolate and characterize the fucose-containing molecule which is present in cone outer segments but absent in rod outer segments of certain species and to determine if it represents a cone visual pigment. The parameters of shedding of cone outer segment tips will be characterized using electron microscopic and radioautographic techniques. The morphologic pattern and time-course of membrane renewal and turnover in cone outer segments will be documented using staining, radioautographic and freeze fracture techniques at the electron microscope level. Rod and cone outer segment renewal will be studied in the cat retina following photoreceptor damage in experimental commotio retinae and the pattern of breakdown of the blood retinal barrier following this injury will be examined. Early stages of hereditary glaucoma in rabbits will be examined with respect to fine structure and axonal transport alterations in the optic nerve head. The relative contribution of mechanical factors in the etiology of optic nerve head damage in this model for hereditary glaucoma will be tested and the deleterious effects of transport alterations on the ganglion cells of the retina will be documented.