Figure 1
From: An assessment of microvascular hemodynamics in human macula
Use of knowledge of macular microvascular histology to evaluate the OCTA image. (a) Average of several aligned OCT angiograms (OCTA frames) from a normal subject. The FAZ is denoted “F” in (a), (b), (c) and (d). (b) Vessel centreline CoV map of the macular microvascular network from the same subject. The colour bar indicates CoV values capped at 50%, i.e., values greater than or equal to 50% have been assigned the red colour at the top of the colour bar. This has been done to accentuate the differences in CoV values (differences in colour). The visualisation shows that the major radial arterioles and venules appear blue in colour (indicating relatively low CoV) while the capillary network along the radial arterioles or venules including the tiny branches from arterioles and venules appear greenish to reddish (indicating high CoV). Interestingly there are some colour differences between each radial arteriole and venule and these colour differences are more obvious in some regions. (c) Confocal images (depth color-coded 2D projection through the image stack) of retinal microvasculature at the macular region obtained from a donor eye after perfusion staining labelled for filamentous actin. The foveola, fovea, and parafovea regions are indicated by three concentric circles (yellow, red and green respectively). Capillary density in the foveal region is less than that in the parafoveal region27,28. (d) A higher magnification image of the foveal region from (c) showing arterioles “a”, venules “v” and the subsequent branching of the retinal arteriole “a-3” into smaller arterioles “a-2” and “a-1” and capillaries “c”. Two capillaries “c” join to form a first order arteriole “a-1”, and two “a-1” arterioles join to form a second order arteriole “a-2”. The capillaries branching off the retinal arterioles are predominantly in the superficial half of the image stack (red pseudocolour) before connecting to the capillaries draining towards the retinal venules lying in the deeper half of the stack (green pseudocolour). Foveolar area is in the avascular region. Only some of the pairs of arterioles and venules enter the foveal region27,28.
