Quantitative Confocal Imaging of the Retinal Microvasculature in the Human Retina

Abstract

PURPOSE. We investigated quantitatively the distribution of blood vessels in different neural layers of the human retina. METHODS.A total of 16 human donor eyes was perfusion-fixed and labeled for endothelial f-actin. Retinal eccentricity located 3 mm superior to the optic disk was studied using confocal scanning laser microscopy. Immunohistochemical methods applied to whole-mount and transverse sections were used to colocalize capillary networks with neuronal elements. Capillary morphometry, diameter, and density measurements were compared among networks.RESULTS. Four different capillary networks were identified and quantified in the following regions: Nerve fiber layer (NFL), retinal ganglion cell (RGC) layer, border of the inner plexiform layer (IPL) and superficial boundary of the inner nuclear layer (INL), and boundary of the deep INL and outer plexiform layer. The innermost and outermost capillary networks demonstrated a laminar configuration, while IPL and deep INL networks displayed a complex three-dimensional configuration. Capillary diameter in RGC and IPL networks were significantly less than in other networks. Capillary density was greatest in the RGC network (26.74%), and was significantly greater than in the NFL (13.69%), IPL (11.28%), and deep INL (16.12%) networks. CONCLUSIONS.The unique metabolic demands of neuronal subcompartments may influence the morphometric features of regional capillary networks. Differences in capillary diameter and density between networks may have important correlations with neuronal function in the human retina. These findings may be important for understanding pathogenic mechanisms in retinal vascular disease. (Invest Ophthalmol Vis Sci. 2012;53:5728-5736)

The 3D Retinal Capillary Circulation in Pigs Reveals a Predominant Serial Organization

“…The major differences are the presence in humans of a central retinal artery (instead of several cilioretinal arteries in pigs), the deeper location of retinal arteries 7 and the macula with its central avascular zone. Yet, at the level of small vessels there seems to be a remarkable similarity between pigs and humans; close to the human optic nerve, Tan et al 10 identified four layers of retinal microvessels, the patterns of which were similar to those we found. Also, images of the human DVP obtained by OCTA 22 showed a similar pattern to that we found in pigs.…”

“…For instance, capillaries connected to precapillary arterioles in the SVP were assumed to have a flow centrifugal to the SVP, while those in the DVP were assumed to have a flow directed toward the center of watersheds; that is, toward transverse venules. Indeed, the DVP in pigs had a very similar aspect to that of mice, 6 rats, 7 and humans 10,21 ; that is, a mosaic of anastomotic watersheds. Therefore, it was assumed that the DVP had a similar organization of capillaries converging toward central venules.…”

Optical coherence tomographic angiography shows reduced deep capillary flow in paracentral acute middle maculopathy

“…[5][6][7] Due to close proximity, OCTA segments of the SCP include flow signals from the nerve fiber layer and GCL; segments of the DCP include signals from the intermediate plexus. OCTA distinguishes the SCP from the DCP, where the depth resolution of FA is limited by vertical summation.…”

Projection-resolved optical coherence tomographic angiography

“…We know from previous histological studies that there are three vascular plexuses in human macula (except in the immediate peripapillary region where there are four) [23,[31][32][33][34]. The superficial retinal vascular plexus is in the nerve fiber layer (NFL), ganglion cell layer (GCL), and the superficial portion of the inner plexiform layer (IPL).…”