Background: Primary open angle glaucoma (POAG) is an optic neuropathy characterized by progressive degeneration of retinal ganglion cells (RGC) and their  axons, which results in characteristic excavation of the neuroretinal rim with corresponding visual field (VF) deficits. Optical coherence tomography angiography (OCTA) is a novel imaging modality that can detect vascular flow of the retina and choroid in great detail. The ability to segment OCT angiograms into the different vascular layers may improve understanding of disease pathogenesis.
Objective: To evaluate the correlation between Ganglion Cell and Inner Plexiform Layers thickness using optical coherence tomography (OCT) and the macular microvasculature  density in different stages of primary open angle glaucoma using optical coherence tomography angiography (OCTA).
Subjects and Methods: The study was performed on 80 eyes of 48 subjects including 20 eyes of 11 controls, and 60 eyes of 37 POAG cases which were divided into 3 groups according to Hodapp,Parish,Anderson (H-P-A) classification; Group1: mild glaucoma (20 eyes), Group 2: moderate glaucoma (20 eyes),Group 3: severe glaucoma (20 eyes).
Results: In our study, we found that there was a significant reduction in Ganglion Cell - Inner Plexiform Layer (GCIPL) thickness and macular VD in patients with POAG which increased with increasing glaucoma severity, also we found that OCT and OCTA parametrs were significantly differentiate between normal and POAG cases and also between different stages of POAG.
     Also we found that an OCTA was an important diagnostic tool in diagnosing mild cases of POAG and to differentiate between mild and moderate cases of POAG,in contrast to OCT in which there was no significant differance between mild and moderate cases of POAG. OCTA seems to be a good candidate for diagnosis and follow-up of glaucoma, complementing the results provided by OCT and visual field testing.
Conclusion: Significant differences between eyes with POAG and normal eyes in terms of the macular GCIPL thickness and microvasculature density (VD) suggest that the macular GCIPL thickness and the retinal capillary vessel area density may be reliable indicators of glaucoma severity.