Background: Glaucoma pathogenesis is related to vascular affection. Optical coherence tomography-angiography (OCT-A) is the latest noninvasive imaging techniques for studying the retinal vasculature, optic nerve, and peripapillary region. Glaucoma is related to the reduction of ocular blood flow. Objective: Assessment of the retinal microvasculature changes including the vascular density of macular and radial peripapillary capillary (RPC) in eyes with primary open-angle glaucoma (POAG) using OCT-A. Subjects and Methods: The study included 44 eyes that were divided into two groups. Group 1 included22 eyes healthy subjects as control group and group 2 that contained22 eyes of POAG patients. All were subjected to history, complete ophthalmological examination including refraction, BCVA, slit-lamp, indirect ophthalmoscopy, gonioscopy, applanation tonometry. Investigations were applied; Visual Field (Carl Zeiss Humphrey A3), OCT, retinal nerve fiber layer thinning (RNFLT) & ganglion cell complex (GCC) thickness. (Triton, Topcon) and study tool Swept-Source OCT-A. (Triton, Topcon). Quantitative analysis software; GNU Image Manipulation Program (GIMP). Program V.2.10.8 software. Results: The results showed a statistically significant decrease in vessel density (VD) in the peripapillary region (P<0.001) and both, superficial (P<0.001) and deep (P=0.001) macular regions in POAG subjects. So, the functional damage (VD) was associated with more pronounced structural damage (RNFLT, GCC).  Conclusion: The peripapillary and superficial macular VD outperformed the deep macular VD, as a diagnostic test differentiating between POAG and healthy eyes. The present study found the OCT-A assessment of peripapillary, and macular VD have a good value in monitoring of microcirculation changes in POAG & explaining the relationship between ocular microcirculation and glaucoma pathophysiology.