Figure 1.

Illustration of manual mask generation and cropping processes: (a) original retinal image, (b) mask for manually segmented arteries (yellow) and veins (gray) overlaid on the original image. Optic disc (OD) center is marked with a green “x”, (c) generation of circular crops where each circle is centered at the OD center with diameters ranging from 1 to 6 disc diameters (DD), and (d) generation of rectangular crops maintaining an aspect ratio of 3 × 4 DD. Rectangles were drawn to capture more temporal (75%) than nasal (25%) vessels. Superior and inferior vessels were captured equally.