Longitudinal evaluation of optical coherence tomography parameters for detecting glaucoma progression across disease severities

To evaluate the longitudinal performance of multiple Optical Coherence Tomography (OCT) parameters in detecting glaucoma progression and compare their effectiveness with visual field (VF) parameters across disease stages. In this longitudinal study, 59 glaucoma patients (mean follow-up: 8.51 years) underwent ≥ 5 serial OCT and VF assessments. Primary structural parameters included global RNFL, macular ganglion cell layer (mGCL) and macular retinal thickness (mRT). Progression was defined by significant thinning trends (OCT) or worsening VF indices: mean deviation or pattern standard deviation. Detection rates were compared overall and by disease severity and evaluated using survival analysis. OCT detected progression in significantly more eyes than VF (84.7% vs. 45.8%; p < 0.001). Among structural measures, mGCL demonstrated the highest progression detection rate (61.0%), followed by global RNFL (59.3%) and mRT (57.6%). In mild glaucoma, OCT significantly outperformed VF (87.5% vs. 50.0%; p < 0.001), with mGCL and inferior mRT demonstrating greater sensitivity at earlier stages (p < 0.05). In moderate-to-severe disease, OCT detection remained higher, though not statistically significant. Survival analysis demonstrated earlier and more frequent progression detection with OCT, with divergence increasing over time. By 10 years, structural parameters identified more progressing eyes than VF (57.0% vs. 38.6%). Combining structural and functional criteria did not significantly improve detection beyond OCT alone. Long-term trend-based analysis demonstrates that structural OCT parameters detect glaucoma progression earlier and more frequently than VF testing, particularly in mild disease. These findings support prioritizing mGCL analysis alongside traditional RNFL imaging in routine glaucoma monitoring.