Chen MJ, et al. - Authors estimated 67 subjects using Cirrus spectral domain optical coherence tomography (OCT) to analyze the diagnostic ability of macular ganglion cell asymmetry in the diagnosis of preperimetric glaucoma (PPG). They calculated circumpapillary RNFL (cpRNFL) thickness, macular ganglion cell-inner plexiform layer (GCIPL) thickness and optic nerve head (ONH) parameters using OCT. They observed inferotemporal (IT)/superonasal (SN) asymmetry index with the highest diagnostic sensitivity at 90 and 95% specificities. They also calculated the largest pAUROC value of IT/SN asymmetry index. They found GCIPL asymmetry measurements with a good diagnostic ability for PPG as compared to cpRNFL, GCIPL, and ONH analysis. They preferred IT/SN asymmetry index as a new parameter to identify early structural changes in PPG.