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 γ-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 γ-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 β-parapapillary atrophy, and to measure areas of the β-zones (area with intact Bruch's membrane) and γ-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 γ-zone, whereas none of the healthy control eyes showed MvD. MvD was universally identified within the γ-zone and additionally involved the β-zone in eyes with both γ- and β-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 γ-zones (P ≤ 0.010) and β-zones (P ≤ 0.005) on the presence of MvD. Conclusions MvD was frequently identified in the γ-zone in POAG eyes, but not in healthy eyes. Worse visual field loss and larger areas of γ- and β-zones were associated with the presence of MvD in POAG eyes with a parapapillary γ-zone.