Magnitude of Diurnal Change in Retinal Vessel Density: Comparison Between Exfoliative Glaucoma and Primary Open-Angle Glaucoma

OBJECTIVES: The aim of this study was to investigate the magnitude of diurnal fluctuation in the superficial parafoveal vessel density (pfVD) and radial peripapillary capillary-peripapillary vessel density (RPC-ppVD) in exfoliative glaucoma (XFG) patients using optical coherence tomography angiography (OCTA) and to compare the findings with those of primary open-angle glaucoma (POAG) patients with glaucomatous damage of comparable severity. METHODS: A total of 50 patients with XFG and 48 with POAG were examined in this retrospective cross-sectional study. The OCTA readings and intraocular pressure (IOP) values were obtained at 9 am, 11 am, 2 pm, and 4 pm on the same day. The maximal change in the IOP and vessel density (VD) values was evaluated to determine the magnitude of diurnal variation. RESULTS: No significant difference was found in the magnitude of the average diurnal superficial-pfVD, RPC-ppVD and IOP change between the XFG and POAG groups. Comparison of the diurnal variation of sub-sector VD revealed that the magnitude of the diurnal variation in the VD of the inferonasal peripapillary and superior parafoveal regions was greater in the XFG group than that of the POAG group (p=0.004 and p=0.021, respectively). Furthermore, the differences persisted after correcting for the confounding factors of IOP, mean deviation (MD), and global retinal nerve fiber layer (RNFL) values. The magnitude of the average superficial-pfVD and the average RPC-ppVD was not correlated with the MD, total ganglion cell complex, global RNFL, or the magnitude of IOP values in either group. CONCLUSION: The eyes of XFG patients demonstrated more significant diurnal fluctuation in VD (including the superior superficial-pfVD as well as the inferonasal RPC-ppVD) when compared with POAG patients, despite no statistical significance between groups in the IOP variation.