Purpose: To evaluate the functional changes in various morphologic types of idiopathic epiretinal membrane (ERM) by multifocal electroretinography (mfERG) and spectral-domain optical coherence tomography (SD-OCT).
Methods: All patients (n = 71) with unilateral idiopathic ERM underwent complete ophthalmologic examination, including measurements of best-corrected visual acuity (BCVA), SD-OCT, and mfERG for both eyes. To classify idiopathic ERM by subtype, the morphologic characteristics of the foveal area on representative scanned images were assessed. The five subtypes by foveal SD-OCT morphology included fovea-attached ERM with outer retinal thickening and minimal inner retinal change (Group 1A), outer retinal inward projection and inner retinal thickening (Group 1B), and prominent thickening of inner retinal layer (Group 1C) and foveal sparing ERM with formation of macular pseudohole (Group 2A) and with schisislike, intraretinal splitting (Group 2B).
Results: On mfERG, P1 amplitude density in the central ring (R1) and inter-eye (affected eye/fellow eye) response ratio of P1 amplitude density in R1 differed significantly among five groups (P = 0.032 and P = 0.022, respectively). In Group 1 patients, central subfield thickness (CST) and inner retinal layer thickness (IRT) on SD-OCT were strongly correlated with BCVA and P1 amplitude density in R1. A receiver operating characteristic (ROC) curve analysis showed that IRT had high predictive accuracy in distinguishing Groups 1A and 1B (area under the ROC curve [AUROC] = 0.966) and Groups 1B and 1C (AUROC = 1.000).
Conclusions: Multifocal electroretinography can be used to investigate the pathophysiology of ERM and to evaluate the degree of functional demise in the fovea on SD-OCT.