Purpose: To determine the prognostic significance of choroidal microvasculature dropout (MvD) to predict the future rate of progressive retinal nerve fiber layer (RNFL) thinning in eyes with primary open-angle glaucoma (POAG).

Design: Prospective, longitudinal case series. Participants: This study enrolled 101 eyes of 101 patients with POAG who underwent OCT angiography (OCTA) imaging of the optic nerve head at baseline and were followed up for at least 2 years thereafter, during which RNFL thickness was measured by serial spectral-domain OCT.

Methods: The peripapillary microvasculature was evaluated by examining en face OCTA images. Choroidal MvD was defined as a focal sectoral capillary dropout with no visible microvascular network in the choroidal layer. The rate of RNFL thinning was determined by linear regression of serial OCT RNFL thickness measurements. Main outcome measures: Influence of the presence of an MvD on the rate of subsequent RNFL thinning.

Results: Microvasculature dropout was identified in 48 eyes (47.5%). The rate of global RNFL thinning was significantly faster in eyes with MvD than eyes without MvD (-1.6±0.8 vs. -1.2±0.9 μm/year, P = 0.018). Eyes with MvD in the inferior hemisphere (n = 41) showed a faster rate of inferior RNFL thinning than eyes without MvD (P = 0.036). Eyes with MvD in both the superior and inferior hemispheres (n = 5) showed faster rates of superior (P = 0.027) and inferior (P = 0.016) RNFL thinning than eyes without MvD. Multivariate regression analysis showed that MvD at baseline (P = 0.003) and the presence of disc hemorrhage during follow-up (P = 0.001) were independently associated with a faster rate of global RNFL thinning.

Conclusions: Microvasculature dropout was an independent predictor of a faster rate of progressive RNFL thinning in patients with POAG. Microvasculature dropout location was topographically associated with the location of faster RNFL thinning.