Figure 1. Vascular geometry of the choriocapillaris in man.

Portions of human choriocapillaris in the posterior pole are shown from the retinal side in (a,b,e) and from the scleral side in (c,d). Shown in (b,c,d) are three-dimensional reconstructions of portions of choriocapillaris obtained by serially imaging the vascular plexus at different depths. The capillaries are separated by collagenous pillars spanning the thickness of the choriocapillaris (arrow, a, b). In (c), two venules are seen inserting into the plane of the capillaries at approximately a right angle (arrows). (d) Arterioles and venules inserting into the plane of the choriocapillaris may be differentiated by the morphology of their endothelial cells, which is characteristically more elongated in arterioles (red arrows) and more rhombic in venules (blue arrow). Shown in (e) is the distribution of arteriolar (red dots) and venular (blue dots) openings, which correspond to insertions of respectively feeding arterioles and draining venules into the outer surface of the choriocapillaris, over an extended portion of tissue taken from the posterior pole. The number of arteriolar openings is here N_a = 73; the number of venular openings is N_v = 59.