Retinal nutritive systems in vertebrates

The components of retinal nutritive systems show considerable variation throughout the vertebrates. In all species studies, there is a choroidal system that lies just sclerad (external) to the retina. Vitread (internal) epiretinal (or preretinal) systems are present in a variety of species, as are intraretinal vessel systems; complete lack of these latter two mentioned systems is also observed in some species. In this presentation, I describe the morphologic characteristics of retinal nutritive systems of fish, reptilian avian, and various mammalian species. A number of these variations are demonstrated photographically through the use of fundus photography. In particular, I describe and provide examples of holangiotic, merangiotic, paurangiotic, and anangiotic retinal vascular patterns within the eyes of mammalian species.