To investigate the association between ocular/systemic factors and visual acuity decline in glaucoma patients with loss of ganglion cell complex thickness (GCCT). In 515 eyes of 515 patients with open-angle glaucoma (mean age, 62.6 ± 12.8 years; mean deviation, -10.95 ± 9.07 dB), we used swept-source optical coherence tomography to measure macular GCCT in sectors classified as corresponding to circumpapillary retinal nerve fiber layer clock-hour sectors from 7 o'clock (inferotemporal) to 11 o'clock (superotemporal). We calculated Spearman's rank correlation coefficient between each sector and best-corrected visual acuity (BCVA), determined cutoff values for BCVA decline (<20/25), and used multivariable linear regression models to determine the correlation between BCVA and biological antioxidant potential (BAP), corneal hysteresis (CH), and temporal-tissue optic nerve head blood flow (represented by temporal mean blur rate, or MBR-T). Macular GCCT corresponding to the 9 o'clock sector had the highest correlation with BCVA (Rs = -0.454; P < 0.001) and a cutoff of 76.17 µm (area under the receiver operating characteristic curve = 0.891; P < 0.001). Subjects below this cutoff (N = 173) showed significant correlations between BCVA and age, BAP, CH, and MBR-T (β = 0.192, P = 0.033; β = -0.186, P = 0.028; β = -0.217, P = 0.011; and β = -0.222, P = 0.010, respectively). Multiple factors are involved in BCVA decline in patients with glaucoma with decreased macular GCCT. This suggests that evaluating BCVA may require assessing multiple factors. Multiple factors contribute to BCVA decline.