Objective: To investigate the diagnostic performance of layer-by-layer segmented macular ganglion cell complex (GCC) thickness for detecting early glaucoma using spectral-domain optical coherence tomography (SD-OCT) with different macular grids.

Methods: Sixty-two early-stage open-angle glaucoma patients and 70 healthy subjects were enrolled in this study. The SD-OCT with automated segmentation was used to obtain macular scans with different grids of "1, 2, and 3 mm"; "1, 2.22, and 3.45 mm"; and "1, 3, and 6 mm" diameters. The separate thicknesses of the macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), ganglion cell-inner plexiform layer (GCIPL: GCL+IPL), and GCC (RNFL+GCL+IPL) were measured in each grid. The areas under the receiver operating characteristics were used to compare their specific diagnostic abilities.

Results: In all macular grid diameters, the mRNFL, GCL, and IPL thicknesses, except mRNFL in the 1 to 2 mm macular grid, were significantly thinner in patients with early glaucoma than in healthy subjects. The GCC and GCL in the 3 to 6 mm macular grid diameters were best able to discriminate between early glaucoma and normal groups. When including quadrant parameters in the 3 to 6 mm macular grid diameter, the temporal GCL had the largest areas under the curve of receiver operating characteristics (0.906).

Conclusions: Large macular grids have generally high discriminating power for the diagnosis of early glaucoma by SD-OCT. The GCL or GCC thickness in 3 to 6 mm macular grid could be useful for the identification of early glaucomatous structural loss.