Recent research indicates that the photoreceptors of the retina are highly dependent upon the retinal pigment epithelium (RPE). The interface between the RPE and light receptors is a complex network of macromolecules, the interphotoreceptor matrix (IPM). The IPM surrounds the outer segments of the light receptors and any nutrient or waste product must pass through it. The IMP also contains macromolecules necessary for retinal adhesion to the RPE which prevent retinal detachment. The primary objective of this research is to analyze the organization and components of the IPM in an unusual retina, the cone-dominant retina of the ground squirrel. Undergraduate students will be trained in light- and electron- microscopic techniques as well as biochemical studies. Because of its high cone density, the ground squirrel retina can serve as a model of the foveal area of primate and human retinas. The IPM domains associated with blue- and green-sensitive cones will be analyzed for their anatomical and biochemical differences in an effort to determine which features they share with other mammals and which may be unique to the ground squirrel retina, itself. Insights gained from these studies will supplement studies of the primate retina and fovea and should prove relevant to the human retina.