Influence of choroidal microvasculature dropout on progressive retinal nerve fibre layer thinning in primary open-angle glaucoma: comparison of parapapillary -zones and -zones

Background/aimsTo compare the influence of choroidal microvasculature dropout (cMvD) on progressive retinal nerve fibre layer (RNFL) thinning in glaucomatous eyes with parapapillary beta-zones and gamma-zones. Methods294 eyes with primary open-angle glaucoma (POAG) and parapapillary atrophy (PPA) underwent optical coherence tomography (OCT) to determine the type of PPA and OCT angiography scanning of the optic nerve head to determine the presence of cMvD. Eyes were classified based on the type of PPA (beta-zones and gamma-zones), and their clinical characteristics were compared. Factors associated with the rate of rapid progressive RNFL thinning were determined in each group, including the presence of cMvD as an independent variable. ResultsOf the 294 eyes, 186 and 108 were classified as having beta-zones and gamma-zones, respectively. The rate of RNFL thinning was slower (p<0.001), axial length was longer (p<0.001) and presence of cMvD was less frequent (57.4% vs 73.1%, p=0.006) in eyes with gamma-zone than those with beta-zone. Multivariate analyses showed that greater lamina cribrosa curvature (p=0.047) and the presence of cMvD (p=0.010) were associated with a faster rate of RNFL thinning in eyes with beta-zone, whereas larger intraocular pressure fluctuation (p<0.001), shorter axial length (p=0.042) and greater baseline RNFL thickness (p<0.001) were associated with a faster rate of RNFL thinning in eyes with gamma-zone. ConclusionsThe presence of cMvD was significantly associated with a faster rate of RNFL thinning in POAG eyes with beta-zone, but not gamma-zone. The pathogenic consequences of cMvD in POAG eyes may depend on accompanying peripapillary structures.