Digital red-free photography for the evaluation of retinal blood vessel displacement in epiretinal membrane

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 idiopat hic 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 fund us using the Topcon Imagenet-1024 System. Photographs were taken on entry t o 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 m acula on follow-up examinations. To clearly visualize vessel shift, both ph otographs of each patient were overlaid using the peripheral landmarks of m ajor blood vessel crossings as reference points. Main Outcome Measures: The parameters measured were shifting of blood vesse ls 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 mu m-434 mu m) was noted in all 13 e yes, but in 15 measurements the shift was less than 30 mu m and was conside red as no shift. In four eyes (31%), the distances decreased in all directi ons, indicating contraction of the ERM. In four eyes (31%), the distances i ncreased 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 ey es (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 too l for the objective measurement of the vessel displacement during ERM forma tion. Contraction and release of the ERM were noted.