To characterize OCT angiography (OCT-A) vessel density of patients with primary open-angle glaucoma (POAG) with unilateral visual field (VF) loss. Cross-sectional study. A total of 33 patients with POAG with a VF defect in 1 eye (mean VF mean deviation [MD], -3.9±3.1 decibels [dB]) and normal VF in the other eye (mean VF MD, -0.2±0.9 dB) and 33 healthy eyes. All subjects underwent OCT-A imaging, spectral-domain (SD)-OCT imaging, and VF testing. OCT-A retinal vascular measurements were summarized as whole image vessel density (wiVD), circumpapillary vessel density (cpVD), and parafoveal vessel density (pfVD). Inter-eye differences in vascular measures, as well as SD OCT retinal nerve fiber layer (RNFL), macular ganglion cell complex (mGCC) thickness, and rim area measurements in glaucoma and healthy eyes were compared. Areas under the receiver operating characteristic curves (AUROCs) were used to evaluate diagnostic accuracy for differentiating between unaffected eyes of patients with POAG and healthy eyes. Difference in OCT-A vessel density and SD OCT structural parameters between unaffected eyes of patients with POAG with the fellow affected eyes and healthy controls. Mean wiVD in unaffected eyes of patients with POAG (52.0%) was higher than in their fellow affected eyes (48.8%) but lower than in healthy eyes (55.9%; P < 0.001). Mean circumpapillary RNFL (cpRNFL) thickness, mGCC thickness, and rim area measurement in unaffected eyes of patients with POAG (87.5 μm, 87.7 μm, and 1.0 mm2) were also higher than those measurements in their fellow eyes (76.5 μm, 79.5 μm, and 0.8 mm2; P < 0.001) and lower than in healthy eyes (98.0 μm, 94.5 μm, and 1.4 mm2; P < 0.001). The AUROCs for differentiating unaffected eyes of patients with POAG from healthy eyes were highest for wiVD (0.84), followed by mGCC (0.78), cpRNFL (0.77), and pfVD (0.69). OCT-A measures detect changes in retinal microvasculature before VF damage is detectable in patients with POAG, and these changes may reflect damage to tissues relevant to the pathophysiology of glaucoma. Longitudinal studies are needed to determine whether OCT-A measures can improve the detection or prediction of the onset and progression of glaucoma. Copyright © 2017 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.