The relative distribution of retinal and choroidal blood in the human retina.

In this paper a model is presented to explain the relative distribution of retinal and choroidal blood to the human retina. According to this model the retina between the inner limiting membrane and the outer limiting membrane is metabolically controlled and nourished by the retinal vasculature, through Muller cells. The retina between the outer limiting membrane and Bruch's membrane is nourished by the choroidal vasculature, through the retinal pigment epithelium. Muller cells have the ability of metabolic uptake from the interphotoreceptor space as demonstrated in pathological situations suchs as central retinal artery occlusion, when both the Muller cell and the photoreceptor nuclei survive. This demonstrates an overlap existing between the two distributions. Neural elements in the retina depend on Muller cells and RPE for metabolic support. It is only reasonable to expect that the cleavage plane between the two blood supplies is the outer limiting membrane, the outer limit of the Muller cell. In this model both the photoreceptor nuclei (the outer nuclear layer) and the foveal retina are assumed to be supplied by retinal. and not choroidal, vasculature. One consequence is that after long standing retinal detachment the photoreceptor outer segments degenerate (since they become deprived of choroidal blood supply) but the outer nuclear layer, nourished by the Muller cell, continues to survive.