Fig. 3

Computation of vessel density in a 20 × 20° macular-centered OCTA image of a 74-year-old cognitively unimpaired high-risk female. a Processed (cropped, vesselness filtered, and Otsu thresholded) image. b Corresponding reversed contrast/negative image. A customized MATLAB script was used to count the number of white pixels in both the original processed (a; designated as vessels) and the reversed contrast images (b; designated as the non-perfused background). The number of pixels was then converted to mm² based on the micron‐to‐pixel ratio in the x and y directions, as computed from the fiducial marks acquired from the HEYEX software as done previously [22,23,24]. The area of white pixels in mm² designated as vessels was then added to that of the background to compute the total area of the image (~ 36 mm²). The vessel density was then computed as the ratio of the area of white pixels designated as vessels (a) to the total area of the image. Scale bar: 200 µm