Rate of Retinal Nerve Fiber Layer Thinning in Glaucomatous Eyes with Optic Disc and Parapapillary Deep-Layer Microvasculature Loss.

Abstract

Microvasculature dropout in the parapapillary choroidal layer was a more important biomarker of glaucomatous nerve fiber layer thinning when it presented with deep-layer microvasculature of the optic disc rather than when it presents by itself. To characterize open-angle glaucoma (OAG) eyes with optic nerve head (ONH) deep-layer microvasculature dropout (MvD-D) and parapapillary choroidal layer microvasculature dropout (MvD-P) and compare their retinal nerve fiber layer (RNFL) thinning rate. This study included 122 OAG eyes that underwent ≥5 serial spectral-domain optical coherence tomography (OCT) scans during a mean follow-up of 5.4 years. Swept-source OCT angiography (SS-OCTA) was used to evaluate MvD-P and MvD-D. Subjects were classified into three groups according to the presence of MvD-P and MvD-D: (1) no dropout (n=37); (2) solely MvD-P (n=40), and (3) both MvD-P and MvD-D (n=45). The RNFL thinning rate was compared among the three groups, and the associated factors were assessed by Cox proportional hazard analysis. RNFL thinning rates were highest in the group with both MvD-P and MvD-D, followed by the group with solely MvD-P and finally by the no dropout group (-0.24 vs. -0.65 vs. -1.20μm/year, P<0.001). Thinner central corneal thickness (hazard ratio [HR]=0.990, P=0.003), presence of disc hemorrhage (HR=1.802, P=0.035), and coexistence of MvD-P and MvD-D (HR=2.941, P<0.001) were the factors associated with RNFL thinning. The coexistence of MvD-P and MvD-D was associated with faster RNFL thinning than MvD-P alone or no dropout, which suggested that observing the optic disc deep microvasculature along with parapapillary choroidal layer using SS-OCTA may be clinically relevant in monitoring glaucoma progression.