This is a prospective, cross-sectional, observational study by the New York Eye and Ear Infirmary, which recruited normal subjects and glaucoma patients with a range of visual field loss representing various degrees of glaucomatous optic neuropathy. A total of 69 normal eyes and 87 glaucomatous eyes were included for the study, of which 71 had primary open-angle glaucoma, six with pseudo-exfoliative glaucoma, two with pigmentary glaucoma, and eight with chronic angle-closure glaucoma. The purpose of the study was to compare the glaucoma diagnostic capability of global and regional macular layer parameters in different-sized grids utilising spectral-domain optical coherence tomography (Spectralis OCT, version 126.96.36.199 + Glaucoma Module Premium Edition software; Heidelberg Engineering, GmbH, Dossenheim, Germany). Serial horizontal scans of the macula were obtained. Automated macular grids with diameters of 3, 3.45 and 6mm were used. For each grid, 10 parameters (total volume and average thicknesses in nine regions) were obtained for five layers: macular retinal nerve fibre layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), ganglion cell and inner plexiform layer (GCIPL=GCL+IPL) and ganglion cell complex multilayer (GCC=mRNFL+GCL+IPL). The authors concluded that isolated macular GCL appears to be as useful as GCC and GCIPL in augmenting glaucoma diagnosis, while IPL alone does not. Nevertheless, although often overlooked, IPL decreases in glaucoma and might have future diagnostic applications. Lastly, larger macular grids performed more accurate glaucomatous analysis, whereas each layer has a characteristic region with maximum glaucoma diagnostic capability.