Comparison of peripapillary capillary plexus using optical coherence tomography angiography and retinal nerve fibre layer analysis using spectral domain optical coherence tomography in glaucoma patients, glaucoma suspects, and healthy subjects

Purpose: To assess the association between radial peripapillary capillary (RPC) plexus using optical coherence tomography angiography (OCTA) and retinal nerve fibre layer (RNFL) thickness using spectral domain OCT (SD-OCT) in primary open-angle glaucoma (POAG) patients, glaucoma suspects, and healthy subjects. Methods: In this single-centre cross-sectional observational study, POAG, glaucoma suspects, and healthy patients underwent OCT-RNFL and optic nerve head angiography scans. The RNFL thickness and the vascular parameters obtained from RPC plexus, including perfusion density (PD), flux index (FI), and vessel density (VD), were analysed. Results: In all, 120 eyes of 120 patients, including 40 POAG patients, 40 glaucoma suspects, and 40 healthy subjects, were included. The pairwise comparison of mean RNFL thickness, FI, and VD showed significant difference ( P < 0.001) in all sectors between POAG, glaucoma suspects, and healthy eyes. However, PD showed no significant difference between glaucoma suspects and healthy eyes. The average RNFL thickness was found to have a better diagnostic ability than VD to distinguish POAG eyes from healthy eyes and glaucoma suspects based on receiver operating characteristics curve and area under the curve. VD had better diagnostic accuracy than RNFL when glaucoma suspects and healthy were compared. Conclusion: OCT-RNFL has better diagnostic capability in differentiating glaucoma from healthy eyes compared to OCTA. However, OCTA was found to be better in screening out glaucoma suspects from healthy eyes. The VD is a better OCTA parameter than FI and PD to differentiate POAG and glaucoma suspects from healthy eyes.