Comparison of GCL and GCIPL Measures for Detection of Early Glaucoma

Abstract

Purpose : Test the hypothesis that macular ganglion cell layer (GCL) measurements are able to detect early damage better than ganglion cell/inner plexiform layer (GCIPL) thickness.

Methods : First cohort included 84 glaucoma eyes with visual field (VF) mean deviation (MD) ≥–6 dB and 129 normal eyes. 8x8 GCL and GCIPL macular grids were exported and 5 superior and inferior macular sectors were defined (Figure 1). Areas-under-ROC curves (AUC) for sectoral GCL and GCIPL measures were compared.
A second cohort of 98 glaucoma and 48 normal/glaucoma suspect (GS) eyes with GMPE macular scans had GCL/GCIPL deviation maps analyzed. Proportion of areas with abnormal (<5%/1% cutoffs) and supernormal thickness (>95%/99%ile cutoff) was estimated on deviation maps (Figure 2). Differences in extent of abnormal and supernormal regions were compared in glaucoma and normal/GS subjects.

Results : In the first cohort, average VF MD was –3.0±1.8 dB in glaucoma eyes. Inferior sector 2 thickness performed best for detection of glaucoma with both GCL and GCIPL (AUCs=0.895; p>0.05). VF MD was –2.3±1.7 dB in glaucoma eyes in the second cohort. In the central elliptical area, extent of GCL damage at <5% and 1% cutoffs was 27.4%±26.0% and 15.2%±20.6% vs. 26.7%±26.4% and 14.6%±20.6% for GCIPL, respectively, in glaucoma eyes (p=0.01 and =0.02, Figure 2a); the extent of GCL and GCIPL supernormal regions were similar (p=0.87). In normal eyes, extent of GCL abnormality at 5% and 1% cutoffs were 16.0%±18.9% and 5.9%±10.7% vs. 15.0%±18.4% and 5.3%±10.5% for GCIPL (p=0.07 and =0.01); GCL and GCIPL supernormal areas were similar (p=0.93). Results for the entire scan area were similar (Figure 2b). Extent of abnormality at <1% cutoff best predicted glaucoma (AUC=0.730 vs. 0.700 for GCL vs. GCIPL).

Conclusions : Macular GCL deviation maps are more likely than GCIPL to flag abnormality with acceptable specificity; however, the difference is clinically unremarkable. GCL and GCIPL sectoral thickness are equivalent for detection of glaucoma.

This is a 2021 ARVO Annual Meeting abstract.