Influence of Epiretinal Membranes on the Retinal Nerve Fiber Layer Thickness Measured by Spectral Domain Optical Coherence Tomography in Glaucoma

PURPOSE: We investigated changes in the thickness of the peripapillary retinal nerve fiber layer (RNFL) following the onset of an epiretinal membrane (ERM) in glaucoma patients. METHODS: Among regularly monitored glaucoma patients, patients with a newly diagnosed ERM were consecutively enrolled. Before and after the onset of ERM, the RNFL thickness was measured using spectral domain optical coherence tomography, and a visual field examination was performed using a Humphrey field analyzer. Changes in RNFL thickness parameters and global indices of the visual field analyzer were assessed. RESULTS: In a total of 28 eyes from 28 patients, the average RNFL thickness increased by a mean of 4.0 ± 7.4 µm (p = 0.009) after ERM onset. There was an increase in the superior, nasal, and temporal quadrant RNFL thicknesses, and the change in the temporal RNFL thickness was significant (14.4 ± 21.2 µm, p < 0.001). However, the inferior RNFL thickness decreased by −0.6 ± 7.5 µm (p = 0.116). In the visual field examination, the mean deviation decreased significantly by −0.8 ± 1.7 dB (p = 0.038), from −14.6 to −15.4 dB. CONCLUSIONS: A significant increase in average RNFL thickness was detected following ERM onset in glaucoma patients, although there was deterioration of the mean deviation in the visual field. When ERM occurs in glaucoma patients, clinicians should be aware that RNFL thickness measurements obtained with a spectral domain optical coherence tomography may underestimate the status of glaucomatous optic neuropathy.