The effect of ectopic inner foveal layer thickness on metamorphopsia in idiopathic epiretinal membranes

PURPOSE: The objective is to determine the effect of ectopic inner foveal layer (EIFL) thickness on preoperative and postoper-ative best-corrected visual acuity (BCVA) and metamorphopsia scores in stage 3 epiretinal membranes (ERM).
METHODS: Thirty eyes of 28 patients were included in the study. All patients underwent uncomplicated vitrectomy and membrane peeling. EIFL, central foveal thickness (CFT), outer nuclear layer (ONL), inner nuclear layer (INL), inner plexiform layer (IPL) thicknesses were measured preoperatively and postoperatively at 3 months using Spectralis spectral-domain optical cohorence tomography. Horizontal line (MH) and vertical line (MV) metamorphopsia scores were calculated using M-CHARTS. Postoperative changes in OCT parameters and visual functions and the correlations between them were analyzed.
RESULTS: EIFL thickness, ONL thickness, and CFT were 143.1 ± 19.1 μm, 189.3 ± 48 μm, and 431.7 ± 58 μm preoperatively, respectively. In the postoperative 3rd month, they were 131.2 ± 17.3 μm, 163.5 ± 45.1 μm, and 388.2 ± 52.6 μm (P = 0.004, P = 0.001, P = 0.001 respectively). BCVA (logMAR: Logarithm of the minimal angle of resolution), MH, and MV scores at the postoperative 3rd month were significantly lower than their preoperative values (P < 0.001 in all three). Preoperative CFT was found to be correlated with preoperative MH and MV (P = 0.031, P = 0.02, respectively). Preoperative ONL thickness was correlated with MH and MV scores (P = 0.049, P = 0.014, respectively). Preoperative INL thickness was only positively correlated with the MH score (P = 0.004). There was no correlation between preoperative - postoperative OCT parameters and postoperative visual functions.
CONCLUSION: EIFL thickness had no effect on metamorphopsia and BCVA in stage 3 ERM patients. It was thought that the formation of metamorphopsia in these patients might be due to changes in the outer retinal layers.