Reevaluation of the optic disk vasculature.

The optic disk vessels of owl monkeys and humans were studied in whole mounts injected with silicone rubber and by serial sections of paraffin-embedded tissue. The capillary bed of the optic nerve head in continuous on one side with the retinal vessels and on the other side with the optic nerve behind the globe. The choriocapillaris is a separate capillary bed, even though it and the disk capillaries are both supplied by branches of the posterior ciliary artery. At the junction between choroid and optic disk is a cuff of vessels that seems equivalent to an anterior extension of the pial vessels. This cuff includes capillaries of the central nervous system, was well as arterial branches of the posterior ciliary artery that pass retrograde from the peripapillary choroid and sclera into the pial plexus. While not contradicting previous descriptions of the vascular anatomy in this region, we emphasized that the microvascular bed of the disk is anatomically an integral part of the retina-optic nerve vascular system and deemphasized its relationship to the choroidal vasculature.