Characteristics of the macular microvasculature.

The morphological appearance and the quantitative analysis of the structure of the macular microvasculature were investigated in 33 normal subjects by fluorescein angiography and stereoscopic mapping techniques. The foveal capillary network was formed by the anastomosis of 4 to 6 groups of terminal arteriolar and venous branches. The inner three rings of capillaries were a single layer of microangium. The apertures of the network differed in size and the closer to the foveal avascular zone, the larger were the apertures. The mean inner width of the capillaries in the fovea was 12.99 +/- 2.2 (SD) microns, and it was 24.55 +/- 6.51 microns on the edge of the fovea. There was a strikingly regular pattern of 4 to 6 arterioles with associated venules. The inner diameter of the smaller vessels on the edge of this area was 35.17 +/- 6.41 microns. In the external perifovea, the arterial and venous branches increased in number to more than 12 and the diameter of these vessels was 4.5 times larger than that of the capillaries in the fovea. The characteristics of the macular microcirculation provide a basis for studying macular disease, particularly the pathogenesis of vascular disorders.