PurposeTo determine the ultra-widefield fluorescein angiographic (UWFA) characteristics of patients with mild familial exudative vitreoretinopathy (FEVR) who had been confirmed to have pathogenic variants of the autosomal dominant (AD) genes of FEVR. DesignSingle center, observational case series. Subjects and ControlsThirty-seven patients with mild FEVR from 27 families who had pathogenic variants of the Norrin/β-catenin genes were studied. The controls consisted of 32 family members who had been confirmed not to carry the pathogenic variants or had heterozygous variants of the autosomal recessive inheritance gene. MethodsSixty-four UWFA images from the patients were compared to 60 UWFA images from the controls. The relative length of the temporal retina to the peripheral avascular retina was determined. The cut-off ratio of the relative lengths for a clinically significant avascular retina (csAR) associated with AD-FEVR was determined using the receiver operating characteristic (ROC) curves. Main Outcome MeasuresThe presence or absence of six peripheral vascular changes: csAR, V-shaped vascular notch, brushy vascular ends, vascular stain, loop vessels and/or anastomosis, and capillary telangiectasia were compared between the patients and the controls. ResultsThe csAR was set at >12% of the length from the ora serrata to the optic disc. The AD-FEVR patients had more frequent retinal changes than the controls for the V-shaped vascular notch (69% vs 2%, P <0.001), brushy vascular ends (78% vs 3%, P <0.001), csAR (83% vs 22%, P <0.001), and vascular stain (70% vs 33%, P <0.001). Loop vessels and/or anastomosis of peripheral vessels were found significantly less frequently in the patients than in the controls (39% vs 73%, P <0.001). No significant difference was found for capillary telangiectasia between the two groups. The combination of the V-shaped vascular notches, brushy vascular ends, and csAR had a sensitivity of 82.8% and specificity of 98.3% with the highest ROC curve of 0.9. ConclusionsThe combination of V-shaped vascular notch, brushy vascular ends, and csAR can be used as a biomarker for AD-FEVR patients who have pathogenic variants of the Norrin/β-catenin genes. These findings will allow more accurate segregation analysis in FEVR families and allow better genetic counseling.