Comparison of Optical Coherence Tomography Angiography Metrics in Primary Angle-Closure Glaucoma and Normal-Tension Glaucoma

Abstract

Purpose: To investigate the peripapillary vascular metrics in early normal tension glaucoma (NTG) and early primary angle closure glaucoma (PACG) eyes using optical coherence tomography angiography (OCT-A).Methods: One or both eyes of each subjects were imaged for a 3x3mm peripapillary region by swept-source OCT-A (DRI-OCT Triton, Topcon, Japan) and assessed by an automated MATLAB program. OCT-A metrics including circumpapillary vessel density (cpVD) and fractal dimension (cpFD) were compared. Their association with visual field (VF) parameters and retinal nerve fiber layer (RNFL) thickness were determined.Results: Sixty-eight eyes of 51 PACG, 68 eyes of 48 NTG, and 68 eyes of 49 control subjects were cross-sectionally analyzed. NTG eyes had significantly lower global cpVD (52.369±0.781%) compared with PACG eyes (55.389±0.721%, P=0.004) that had comparable disease severity and average RNFL thickness. Multivariable analysis reviewed that, for PACG and NTG eyes, decreased cpVD ([PACG] β=-4.242; CI:-8.120, -0.363 vs [NTG] β=-5.531; CI:-9.472, -1.590) and cpFD ([PACG] β=-8.894;CI:-11.925, -5.864 vs [NTG] β=-12.064; CI:-17.095, -6.932) were associated with decreased RNFL thickness (all P≤0.032); with a stronger association between decrease cpFD and decreased RNFL thickness in NTG eyes (Fisher’s Z-test, P=0.045). Decreased cpVD was associated with decrease mean deviation (MD) in NTG eyes (β=-0.707; CI:-1.090, -0.324; P≤0.001) and not associated with the visual field parameters in PACG eyes. Conclusions: Early NTG had lower global cpVD compared with early PACG, despite similar disease severity and average RNFL thickness. Précis:Optical coherence tomography angiography observed a lower peripapillary microvascular perfusion in early NTG eyes compared with early PACG eyes, despite similar disease severity and retinal nerve fiber layer thickness.