GCIPL color coding on OCT predicts glaucoma conversion in normal-tension glaucoma suspects, including a high myopia subgroup

This retrospective study investigated the predictive value of OCT-derived color coding in assessing the risk of glaucoma conversion among normal-tension glaucoma (NTG) suspects, with a particular focus on highly myopic eyes. A total of 307 eyes underwent baseline spectral-domain OCT imaging, with RNFL and GCIPL thicknesses categorized by device-generated color codes (green: normal, yellow: borderline, red: abnormal). Glaucoma conversion was defined by the emergence of reproducible visual field defects over a mean follow-up of 76.0 ± 8.8 months, during which 23.8% of eyes progressed. Inferotemporal GCIPL thickness showed the strongest discriminative capacity (AUC = 0.68, cutoff = 62.0 μm), with further improvement in highly myopic eyes (AUC = 0.85). Red color coding in the inferotemporal sector was associated with a significantly increased risk of conversion (HR 2.473; p = 0.050), while eyes with green coding in both inferotemporal and average GCIPL sectors demonstrated high negative predictive values (85.0% overall, 90.2% in the myopic subgroup). These results highlight the clinical utility of GCIPL color coding on OCT as an accessible and practical tool for identifying early disease stability and stratifying risk of progression, even in anatomically challenging high myopia cases.