Parapapillary Deep-Layer Microvasculature Dropout in Primary Open-Angle Glaucoma Eyes With a Parapapillary γ-Zone

PURPOSE. To explore the clinical characteristics of parapapillary deep-layer microvasculature dropout (MvD) associated with parapapillary gamma-zone in primary open-angle glaucoma (POAG). METHODS. A total of 150 eyes with POAG and 75 age-and axial length-matched control eyes, both having parapapillary gamma-zone as determined by spectral-domain (SD) optical coherence tomography (OCT), were included. Parapapillary MvD was defined as a focal sectoral capillary dropout without any visible microvascular network identified in deep-layer en-face images obtained using swept-source OCT angiography (OCTA). Optic nerve heads were imaged using SD-OCT to examine the microstructure of beta-parapaplllary atrophy, and to measure areas of the beta-zones (area with intact Bruch's membrane) and gamma-zones (area devoid of Bruch's membrane). Factors associated with the presence of MvD were determined using logistic regression analyses. RESULTS. Parapapillary deep-layer MvD was identified in 117 of 150 POAG eyes (78.0%) with a parapapillary gamma-zone, whereas none of the healthy control eyes showed MvD. MvD was universally identified within the gamma-zone and additionally involved the beta-zone in eyes with both gamma-and beta-zones. Multivariate logistic regression analyses showed significant influence of thinner global retinal nerve fiber layer (P = 0.001), worse visual field mean deviation (P < 0.001), as well as larger areas of parapapillary gamma-zones (P < 0.010) and beta-zones (P < 0.005) on the presence of MvD. CONCLUSIONS. MvD was frequently identified in the gamma-zone in POAG eyes, but not in healthy eyes. Worse visual field loss and larger areas of gamma- and beta-zones were associated with the presence of MvD in POAG eyes with a parapapillary gamma-zone.