PURPOSE: To evaluate idiopathic epiretinal membrane (iERM) area changes and the association with visual function in patients with good vision, using confocal scanning laser ophthalmoscopy (cSLO). METHODS: The medical records of patients with iERM with best-corrected visual acuity (BCVA) ≥ 20/25 and a follow-up period ≥ 2 years were reviewed retrospectively. BCVA, metamorphopsia, fundus images using cSLO, and optical coherence tomography images were obtained at baseline and every 6 months. The ERM area and diagonal lengths of the long and short axes were determined. The progression group was defined as eyes with ≥2 lines of loss, and the stable group was defined as eyes with less change. RESULTS: This study included 46 eyes, with 23 eyes in each group. Participants in the progression group were younger (60.7 vs. 65.7 years, P = 0.015) and showed a larger BCVA change (0.20 vs. 0.04, P < 0.001) and greater ERM area decrease (34.2% vs. 11.7%, P < 0.001) during the follow-up period. In the progression group, BCVA reduction was correlated with area decrease (β = 0.571, P = 0.010). No factors were associated with metamorphopsia. In the univariate analysis, ERM area reduction at 6 months was a significant predictor of vision loss (odds ratio, 1.632; P = 0.002). Receiver operating characteristic analysis identified a 7.66% ERM area reduction at 6 months as the optimal cutoff for predicting vision loss (81.8% sensitivity, 82.6% specificity). CONCLUSIONS: ERM area reduction significantly correlates with vision loss in patients with iERM with good vision. Monitoring ERM area changes can help predict disease progression and visual outcomes.