Correlation between Uncorrected Visual Acuity and Macular Distortion in Idiopathic Epiretinal Membrane Patients

PURPOSE: To evaluate the association between degree of retinal abnormalities and uncorrected visual acuity (UCVA) in idiopathic epiretinal membrane (ERM) patients with a small amount of refractive error. METHODS: We retrospectively reviewed 49 eyes (37 patients) of idiopathic ERM patients. We investigated the association between visual acuity and macular status (central macular thickness [CMT], outer retinal integrity score, and inner retinal irregularity index) that was assessed by optical coherence tomography using multiple linear regression analysis. We defined visual acuity difference (VAD) as the difference between UCVA and best-corrected visual acuity (BCVA). We divided patients into two groups according to VAD size and compared clinical characteristics between the two groups. We also investigated factors associated with VAD using multiple linear regression analysis. RESULTS: BCVA showed significant association with CMT and outer retinal integrity score, while UCVA showed significant association with CMT and inner retinal irregularity index. Patients with a large VAD showed a similar level of BCVA compared to the small VAD group (logarithm of the minimum angle of resolution [logMAR], large VAD group 0.11 ± 0.11 vs. small VAD group 0.13 ± 0.12, p = 0.585). However, UCVA was worse (logMAR, large VAD group 0.44 ± 0.14 vs. small VAD group 0.18 ± 0.14, p < 0.001) and inner retinal irregularity was higher (large VAD group 1.06 ± 0.04 vs. small VAD group 1.04 ± 0.03, p < 0.001) in patients with a large VAD. On multiple linear regression analysis, the absolute value of spherical equivalent (standardized coefficient β 0.521, p < 0.001) and inner retinal irregularity index (standardized coefficient β 0.448, p < 0.001) were significantly associated with VAD. CONCLUSIONS: UCVA was associated with inner retinal irregularity in idiopathic ERM patients with a mild degree of refractive error. Inner retinal irregularity was also associated with degree of VAD, suggesting that the effect of refractive error correction is greater in patients with more distorted retina.