Purpose: To describe a modified glaucoma staging system (Modified GSS) based on the visual field index (VFI) and evaluate the performance of the Modified GSS compared with the Bascom Palmer GSS and Enhanced GSS.
Methods: A total of 549 eyes of 549 patients were studied retrospectively. The Modified GSS was used to classify the glaucomatous visual field defects into stage 0 to 5 based on the VFI. The cutoff values for each stage were derived from VFI that were equivalent to mean deviations of -6, -12, -20, and -25 dB by receiver operating characteristic analysis. The staging performances, based on each of three GSSs, were compared with both the Advanced Glaucoma Intervention Study (AGIS) and Collaborative Initial Glaucoma Treatment Study (CIGTS) scores.
Results: The VFI cutoff values calculated for each stage were 81.5, 62.5, 42.5, and 22.5%, respectively. The correlation coefficient of Modified GSS was greater than that of Bascom Palmer GSS (p < 0.001), and correlation coefficients of Modified GSS and Enhanced GSS were equivalent. However, Enhanced GSS tended to classify moderate to severe AGIS and CIGTS scores into higher stages (p < 0.001).
Conclusions: The Modified GSS is easy to use and accurate, and the staging performance is either equal or superior to existing GSSs.