Macular Ganglion Cell Complex versus Peripapillary Retinal Nerve Fiber Layer Analysis for Assessment of Early Glaucoma

Abstract

Purpose: : Evaluation of total macular thickness has been proven to have poor ability to identify early structural damage in glaucoma. We sought to compare the glaucoma discrimination ability of macular inner retinal layer (MIRL) thickness with that of peripapillary retinal nerve fiber layer (RNFL) thickness measured by spectral-domain optical coherence tomography (SD-OCT) in patients with early glaucoma.

Methods: : A total of 67 glaucoma patients (glaucomatous optic neuropathy and visual field defect) and 56 healthy subjects were included. Eyes were classified as early glaucoma based upon a VF mean deviation index better than -6 dB. All patients underwent MIRL thickness measurement [provided by the Ganglion Cell Complex (GCC) scan] and RNFL thickness measurement (3.45 mm scan) by SD-OCT. Whenever both eyes were eligible, one was randomly selected for analysis. Receiver operating characteristic (ROC) curves and sensitivities at fixed specificities were generated for different MIRL and RNFL parameters. Areas under the ROC curves (AUC) of each parameter were compared (Delong Test).

Results: : Average MD for the glaucomatous eyes was -2.5± 1.6 dB. The AUCs for average, superior and inferior MIRL thickness were not significantly different at 0.815, 0.807 and 0.788, respectively (p≥0.18). The AUCs for average, superior and inferior RNFL thickness were also similar at 0.735, 0.728 and 0.697, respectively (p≥0.15). Average MIRL thickness had a significantly larger AUC compared to average RNFL thickness analysis (0.815 vs 0.735; p=0.03). When considering sensitivities at 80% specificity, a higher sensitivity was found for average MIRL thickness (66.7%; cut-off 89.9 µm) compared to average RNFL thickness (62.9%, cut-off 111.8 µm), but this difference was not significant based on 95% confidence intervals (52.5 - 78.9% and 48.7 - 75.7%, respectively).

Conclusions: : MIRL (GCC scan) thickness analysis has a slightly superior ability to discriminate between eyes with early glaucoma and healthy eyes compared to peripapillary RNFL analysis. Different from previous analysis considering total macular thickness, the GCC macular scan seems to be a useful tool for identification of early structural damage in glaucoma.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: clinical