Relation between superficial capillaries and foveal structures in the human retina.

When examining semithin Epon sections of human retinas, it became evident that superficial capillaries showed four different positions, according to the thickness of the ganglion cell layer. For the clear view of the distribution of the position of superficial capillaries, the intrafoveal region was subdivided into four zones, based on the thickness of the ganglion cell layer; the foveola and the A-, B-, and C-zone. The foveola has no ganglion cell layer, and the A-zone has a ganglion cell layer thinner than 15 microns. These regions lack superficial capillaries. In the B-zone, the ganglion cell layer is 15-45 microns thick, and here the superficial capillaries lie in the outer boundary of the ganglion cell layer. The C-zone and parafovea have a ganglion cell layer thicker than 45 microns, and superficial capillaries are present within the ganglion cell layer. The perifovea has a ganglion cell layer 15-45 microns thick. In the temporal perifovea, where the nerve fiber layer is not so distinct, superficial capillaries are located on the outer boundary of the ganglion cell layer. In the other portion of the perifovea, superficial capillaries lie in the inner boundary of the ganglion cell layer. Out of the perifovea, where the ganglion cell layer is thinner than 15 microns, most of superficial capillaries touch both boundaries of the ganglion cell layer. Major retinal vessels touch the ganglion cell layer and lie in the similar position to that of superficial capillaries.