Background Glaucoma is the neuropathy of the optic nerve with accelerated apoptosis of the retinal ganglion cells. Optical coherence tomography angiography provides valuable information about the optic nerve and the retinal circulation as an auxiliary tool for glaucoma diagnosis and optic nerve saving. Purpose To evaluate the performance of optical coherence tomography angiography in distinguishing primary open-angle glaucoma from healthy eyes by measuring the radial peripapillary capillary (RPC) vessel density (VD)% and macular superficial capillary plexus (SCP) VD%. Patients and methods A descriptive prospective cross-sectional case–control study was conducted on 60 participants, who were categorized into two groups: group A (30 patients with primary open-angle glaucoma and group B (30 healthy controls of matched age and sex with group A). Structural (retinal nerve fiber layer and ganglion cell complex thickness), functional (the mean deviation, and pattern standard deviation), and vascular parameters [the VD of RPC in scan 4.5×4.5 mm (in whole image, and the peripapillary region) and macular SCP in scan 6×6 mm] were compared between the two groups. Results Statistically significant decreases of VD of RPC of the whole disk, the peripapillary region, and the macular superficial plexus layer were observed in glaucoma eyes compared with controls (all P