Quantitative analysis of ET-1 immunofluorescence (Fig 3, Panel B) showed that PDR membranes had significantly higher mean pixel intensity (222.4 ± 30.9 arbitrary units) than idiopathic epiretinal membranes (108.5 ± 21.8 arbitrary units; unpaired t-test, p<0.05). This evidence concerns the gene EDN1 and Epiretinal membrane.