Optical coherence tomography angiography (OCTA) scans of a healthy eye and glaucomatous eyes with mild, moderate, and severe damage. The OCTA scans show a dense peripapillary vessel network in the healthy eye, illustrated in red and yellow in the color-coded map. Glaucomatous damage causes a decrease in vessel damage and replacement of the red/yellow areas with blue, indicating either absence of vessels or no flow.