Retinal Circulation

Abstract

A study of the retinal circulation is a study in contrast. Two independent contrasting circulatory systems supply this complex tissue and both are essential for its function. A single artery and vein supply 1, which many vessels serve the other. Functional collaterals are absent in 1, but present in the other. Intramural pericytes are present in 1, and not in the other. The endothelial cells are continuous and closely linked in 1, while profuse large fenestrations interrupt the endothelium of the other. Neutral vasomotor control does not exist in 1, but is present in the other. The arteriovenous O2 difference is very wide in 1 and very narrow in the other, and so on. Perhaps this sandwich of retinal receptor cells between 2 such completely different circulatory systems, reflects the importance of recording the contrasts of light and shadow as they caress this outpost of the brain.