Abstract

The posterior pole of the eye contains the anatomic fovea and foveola. These structures are highly specialized to maximize visual acuity. In foveola, the inner retinal layers down to the outer nuclear layer are displaced forming a pit, which contains the highest density of cones in the retina (147,000 cones per mm²). The retinal capillaries in the area of the fovea typically form concentrically arranged channels ending in a capillary loop approximately 0.5 mm across which outline a capillary-free zone known as the "foveal avascular zone" FAZ(1). The lateral displacement of inner retinal structures, including the retinal vasculature, presumably exists to leave an unobstructed light path to the site of phototransduction, thereby enhancing image quality. Because of the inverted nature of the retina (blood vessels lie between incoming light and the photoreceptors), it is possible for humans to view shadows of their own retinal vessels and their contents. Entoptic methods for their visualization of retinal blood vessels and blood flow were described in the nineteenth century(2), and recently entoptic visualization methods have been use to study the foveal capillary details and the foveal avascular zone (FAZ) size and shape (3-5), foveola vessels (4,6,7), macular blood flow (8,9) and capillary density around the FAZ (10).

© 1996 Optical Society of America