Purpose To evaluate the performance of ganglion cell/inner plexiform layer (GC/IPL) measurements with spectral-domain optical coherence tomography (Cirrus HD-OCT) for detection of early glaucoma and to compare results to retinal nerve fiber layer (RNFL) measurements. Design Cross-sectional prospective diagnostic study. Methods Fifty-nine glaucoma eyes (47 subjects) (mean deviation >–6.0dB) and 91 normal eyes (52 subjects) were enrolled. Patients underwent biometry and peripapillary and macular OCT imaging. Performance of the GC/IPL and RNFL algorithms was evaluated with area under receiver operating characteristic curves (AUC), likelihood ratios, and sensitivities/specificities adjusting for covariates. Combination of best parameters was explored. Results Average (SD) mean deviation in the glaucoma group was –2.5 (1.9) dB. On multivariate analyses, age (p<0.001) and axial length (p=0.03) predicted GC/IPL measurements in normal subjects. No significant correlation was found between average or regional GC/IPL thickness and respective outer retina (OR) thickness measurements (p>0.05). Average RNFL thickness performed better than average GC/IPL measurements for detection of glaucoma (AUC=0.964 vs. 0.937; p=0.04). The best regional measures from each algorithm (inferior quadrant RNFL vs. minimum GC/IPL) had comparable performances (p=0.78). Entering GCIPL/OR ratio into prediction models did not enhance performance of the GC/IPL measures. Combining the best parameters from each algorithm improved detection of glaucoma (p=0.04). Conclusions Regional GC/IPL measures derived from Cirrus HD-OCT performed as well as regional RNFL outcomes for detection of early glaucoma. Using GCIPL/OR ratio did not enhance the performance of GC/IPL parameters. Combining the best measures from the two algorithms improved detection of glaucoma.

Disc-fovea angle measurements demonstrated fair intersession repeatability. While adjusting for DFA improved RNFL prediction limits in some sectors, it did not enhance glaucoma detection.

Correction of RNFL measurements for ocular magnification did not improve prediction limits in normal subjects or enhance the performance of SD-OCT in this group of eyes in which the axial length did not deviate significantly from average values. The cross-sectional area of the RNFL was not related to the optic disc area.

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