Focal Relationship Between Structure and Function Within the Central 10 Degrees in Glaucoma

PURPOSE: To investigate which measurements of inner macular thickness are the most useful for evaluating the focal relationship with visual sensitivity within the central 10° in glaucoma and which layers require correction for retinal ganglion cell (RGC) displacement. METHODS: Sixty eyes of 60 subjects with glaucoma were included. Sensitivity of each test point of 10-2 standard automated perimetry was compared with the thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), GCL+ inner plexiform layer (IPL), and RNFL+GCL+IPL (GCC), with and without RGC displacement, using Spearman's rank correlation coefficients. Visual sensitivity was evaluated by unlogged 1/Lambert (1/L) values. RESULTS: Retinal nerve fiber layer thickness correlated significantly with the sensitivities of all test points except for some in the papillomacular bundle region when adjusting for RGC displacement (rs = 0.287-0.767, P < 0.05). In the central 5.8°, the GCL and (GCL+IPL) thickness correlated significantly with the sensitivities of all test points when adjusting for RGC displacement (GCL: rs = 0.363-0.729, P < 0.01; (GCL+IPL): rs = 0.359-0.715, P < 0.01). The GCC thickness correlated significantly with the sensitivities of all 68 test points when adjusting for RGC displacement (rs = 0.359-0.767, P < 0.01). RGC displacement improved the correlation between sensitivity and GCL, (GCL+IPL), and GCC in the central 4 points (GCL: rs = from 0.270-0.470 to 0.421-0.540; (GCL+IPL): rs = from 0.195-0.450 to 0.381-0.549; GCC: rs = from 0.132-0.449 to 0.359-0.562). CONCLUSIONS: The GCC is the most useful parameter to evaluate structure and function within the central 10° in glaucoma. Adjusting for RGC displacement is essential to evaluate the relationship between structure of the GCL-related layer and function at the central macula.