PurposeTo investigate, using the Dynamic Vessel Analyzer (DVA), the retinal vascular changes that may occur after vitrectomy for idiopathic epiretinal membrane (ERM).MethodsTwenty-six eyes of 13 patients affected by unilateral idiopathic ERM were prospectively analyzed. 13 fellow eyes were used as control. The static (central retinal artery and vein equivalents) and dynamic (after flicker light stimulus) DVA analysis was performed at baseline (1 day before surgery) and 6 months after vitrectomy.ResultsThe static DVA analysis did not highlight any significant change between investigational eyes and controls at baseline and 6 months after surgery. The DVA dynamic analysis showed similar arterial flicker response between cases and controls at baseline (p = 0.3396), but disclosed a significant reduction of the arterial flicker response after surgery in the study eyes compared to fellow eyes (p = 0.0024).No significant changes were appreciated in the venous flicker response after surgery between cases and controls, both at baseline (p = 0.3450) and at the follow-up examination (p = 0.4214).ConclusionsThe physiological flicker-induced vasoconstriction is reduced after vitrectomy in arteries. The oxygen saturation change occurring after vitrectomy might have a role in the vascular tone modification.