Fig. 5. Changes of foveal surface symmetry difference (FSSD) after epiretinal membrane surgery. Group Ⅰ includes patients who went vitrectomy only and group Ⅱ includes patient who went vitrectomy with sulfur hexafluoride (SF6) tamponade. FSSD consistently increased after surgery in both groups. Two groups did not show significant differences of FSSD at baseline and during the follow-up period. *Significant differences compared with baseline within the group, Wilcoxon Signed Rank test.