Reproducibility of VF, OCT, and OCTA in Glaucoma: A Prospective Multi-Visit Study.

Purpose: To quantify the reproducibility of visual field (VF), optical coherence tomography (OCT), and OCT angiography (OCTA) metrics in primary open-angle glaucoma (POAG). Methods: Thirty-eight POAG patients completed five visits over three months without treatment changes. VF, OCT, and OCTA were obtained. Eyes were classified as mild (mean deviation [MD] > -6 dB) or moderate-to-advanced (MD ≤ -6 dB). Reproducibility was assessed using 95% tolerance limits (TL), intraclass correlation coefficient (ICC), and coefficient of variation (CoV). Mixed-effects models identified factors associated with variability. Results: Thirty-eight participants (age 67 ± 9 years) included 56 mild (74%) and 20 moderate-to-advanced (26%) eyes. VF metrics demonstrated severity-dependent increases in variability, with MD TL widening from ±2 to ±4 dB, ICC decreasing from 0.95 to 0.75, and CoV increasing from 16% to 26%. OCTA metrics also showed severity-related variability, particularly for peripapillary perfusion density (CoV 5% to 9%), whereas macular OCTA parameters showed smaller changes (CoV 1% to 2%). OCT structural measures remained stable across severity stages (peripapillary retinal nerve fiber layer [pRNFL] and ganglion cell-inner plexiform layer [mGCIPL] CoV ∼2%). Worse MD predicted greater variability in VF and OCTA metrics (all P ≤ 0.046), whereas older age, longer axial length, and false-negative rate were associated with greater MD variability (all P ≤ 0.022). Conclusions: VF and OCTA metrics showed severity-dependent variability, whereas OCT structural measures remained stable across severity stages. These findings support modality- and severity-specific thresholds for glaucoma progression. Translational Relevance: This study helps clinicians better distinguish true glaucoma progression from normal test variability across VF, OCT, and OCTA measurements.