Relationship between retinal layer thickness and focal macular electroretinogram components after epiretinal membrane surgery

Purpose. To study the effect of epiretinal membrane (ERM) removal on the function and structure of the retina, and to determine whether the functional changes were correlated with the changes in the thickness of different retinal layers. Methods. Focal macular electroretinography (FMERG) and spectral-domain optical coherence tomography (SD-OCT) were performed on 17 eyes of 15 patients before and after ERM surgery. The parafoveal retina was divided into an inner layer, a middle layer, and an outer layer in the OCT images. The thickness of each layer was measured before and after the ERM surgery. The a-wave, b-wave, and oscillatory potentials (OPs) of the FMERGs were analyzed before and after the ERM surgery. Results. The thickness of the inner and middle retinal layers was significantly reduced after surgery (by 39% and 23%, respectively). The mean amplitudes of the b-waves and OPs at 6 months postoperatively were significantly larger than those recorded preoperatively (by 21% and 61%, respectively). The ratios of the pre- to postoperative b-wave and OP amplitudes were correlated with the thickness reduction of the middle retinal layer (b-wave, r = -0.51, P < 0.05; OPs, r = -0.82, P < 0.01). Conclusions. The significant correlations between the reduction in the thickness of the middle retinal layer and increase in the amplitude of the b-waves and OPs suggest that the improvement of macular function after ERM peeling is due to the decrease in the thickness of the middle retinal layer.