Objective: To evaluate the displacement of retinal blood vessels during the natural course of epiretinal membrane (ERM) formation. Design: Consecutive observational case series. Participants: Thirteen patients (13 eyes) diagnosed with unilateral idiopathic ERM and 10 normal fellow eyes of the same patients served as a control group and constituted the study group. Testing: All eyes underwent digital red-free filter photography of the fundus using the Topcon Imagenet-1024 System. Photographs were taken on entry to the study and again after 8 to 13 months. Distances were measured between the major and minor blood vessel junctions at the upper and lower temporal arcades and between the disc margin and vessel junctions temporal to the macula on follow-up examinations. To clearly visualize vessel shift, both photographs of each patient were overlaid using the peripheral landmarks of major blood vessel crossings as reference points. Main Outcome Measures: The parameters measured were shifting of blood vessels caused by the ERM formation. The distances were measured in micrometers using the measurement feature of the Topcon Imagenet System. Results: Blood vessel shift (range, 30 μm-434 μm) was noted in all 13 eyes, but in 15 measurements the shift was less than 30 μm and was considered as no shift. In four eyes (31%), the distances decreased in all directions, indicating contraction of the ERM. In four eyes (31%), the distances increased in all directions, indicating release of the ERMs. A mixed pattern of release and contraction of the ERM in the same eye was noted in five eyes (38%). No shift of blood vessels was noted in the control eyes. Findings on image overlay corresponded with the objective measurements. Conclusions: Noninvasive digital red-free photography is an informative tool for the objective measurement of the vessel displacement during ERM formation. Contraction and release of the ERM were noted.