Spectral-domain optical coherence tomography for early glaucoma assessment: analysis of macular ganglion cell complex versus peripapillary retinal nerve fiber layer

Abstract

Objective We sought to compare the glaucoma discrimination ability of macular inner retinal layer (MIRL) thickness with that of conventional peripapillary retinal nerve fiber layer (pRNFL) thickness as measured by spectral-domain optical coherence tomography (SD-OCT) in patients with early glaucoma. Design Cross-sectional study. Participants We studied 67 patients with early glaucoma (visual field mean deviation index ≥-6 dB), and 56 healthy subjects were prospectively enrolled. Methods All patients underwent MIRL thickness measurement (ganglion cell complex [GCC] scan) and pRNFL thickness measurement (3.45 mm scan) by SD-OCT. Whenever both eyes were eligible, one was randomly selected. Receiver operating characteristic curves and sensitivities at fixed specificities were generated for different parameters. The areas under the receiver operating characteristic curves (AUCs) of each parameter were compared. Results The average mean deviation for the glaucomatous eyes was −2.5 ± 1.6 dB. The AUCs for average (0.815); superior (0.807); and inferior (0.788) MIRL thicknesses were not significantly different ( p ≥ 0.18). The AUCs for average (0.735); superior (0.728); and inferior (0.697) pRNFL thicknesses were also similar ( p ≥ 0.15). Average MIRL thickness had a significantly larger AUC compared to average pRNFL thickness analysis (0.815 vs 0.735; p = 0.03). Sensitivities at 80% specificity for average MIRL and pRNFL thicknesses were 66.7% (cutoff, 89.9 μm) and 62.9% (cutoff, 111.8 μm), respectively. Conclusions The GCC scan showed a similar or even a slightly better ability to discriminate between healthy and early glaucomatous eyes compared to the pRNFL scan. Different from previous analyses considering total macular thickness, the GCC macular scan seems to be a useful tool for identification of early structural damage in patients with glaucoma.