Combination of optic disc rim area and retinal nerve fiber layer thickness for early glaucoma detection by using spectral domain OCT

To compare the diagnostic ability of optic disc rim area (RA), retinal nerve fiber layer thickness (RNFLT), and their combination on sector-based analysis of spectral domain optical coherence tomography (Cirrus OCT) in discriminating subjects with early-stage open angle glaucoma (OAG) from normal subjects. RA and RNFLT of 78 early OAG and 80 normal subjects were measured on Cirrus OCT at the global area, 4 quadrants, 12 clock hours, and 7 + 11 o'clock (a sector that includes 7 and 11 o'clock). A new parameter, RR (a multiplication of the RA and RNFLT) was derived to identify the best combination of the two parameters. Areas under the receiver operating characteristics curves (AUCs) of RA, RNFLT, and RR were compared. AUCs of RA were larger than those of RNFLT at nasal quadrant, at 1-5 o'clock on Cirrus OCT (all P values < 0.05). At the remaining areas, the two parameters were not significantly different on both devices (all P values > 0.05). RR had significantly larger AUCs than those of both RA and RNFLT at 7 + 11 o'clock (0.931 for RA, 0.933 for RNFLT, and 0.968 for RR) and global area (0.914 for RA, 0.905 for RNFLT, and 0.935 for RR), which were the two areas with largest AUCs. RR outperformed both RA and RNFLT of the Cirrus OCT, especially at areas with diagnostic importance. This suggests that combinations of RA and RNFLT by sector-based analysis of Cirrus OCT would be promising to determine early glaucoma.