Expanded Spectrum of Ectopic Inner Foveal Layer in Stage 3 Epiretinal Membrane.

PURPOSE: To assess Ectopic Inner Foveal Layer (EIFL) spectrum in Stage 3 epiretinal membrane (ERM) and to compare the demographic, anatomical, and functional characteristics among groups. METHODS: EIFL was classified into three subtypes based on anatomical OCT features. Patient demographics, BCVA, and structural OCT parameters were collected. Cross-sectional group comparisons, within-subtype correlation analyses, and multinomial logistic regression were performed to assess associations with EIFL subtype classification. RESULTS: Among 114 eyes, three distinct EIFL patterns were identified: nascent EIFL (nEIFL) characterized by minimal EIFL thickness and better BCVA, immature EIFL (iEIFL) showing moderate EIFL thickness with intermediate BCVA, and mature EIFL (mEIFL) demonstrating higher EIFL thickness with poorest BCVA. Large effect sizes were observed between nEIFL and iEIFL (Cohen's d=0.98, p<0.001) and between nEIFL and mEIFL (Cohen's d=0.63, p=0.008) for BCVA. Multinomial Logistic Regression model showed age and EIFL thickness as main predictors of EIFL type (p < 0.001 and p = 0.001 respectively). CONCLUSION: The proposed EIFL subtypes showed distinct cross-sectional morphological and functional profiles in stage 3 ERM. Less extensive EIFL involvement was associated with better BCVA, whereas greater EIFL thickness and older age were associated with classification into more extensive EIFL subtypes. Longitudinal studies are required to determine whether this anatomical spectrum reflects temporal progression and whether it has prognostic value for postoperative anatomical and functional outcomes.