Relationship Between Retinal Fractal Dimension and Non-perfusion in Diabetic Retinopathy on Ultra-Wide Field Fluorescein Angiography

Purpose To correlate fractal dimension (FD) of the retinal vasculature with the extent of retinal non-perfusion area (NPA) in diabetic retinopathy (DR) on ultra-wide field (UWF) fluorescein angiography (FA). Design Cross-sectional study. Methods Baseline Optos 200Tx UWF FA images of 80 eyes with DR from the DAVE (NCT01552408) and RECOVERY (NCT02863354) studies were stereographically projected at the Doheny Image Reading Center. The retinal vasculature was extracted from an early-phase FA frame by exploiting the elongated nature of the vessels and then skeletonized for calculation of FD using a box-counting method. NPA was delineated by two independent, masked reading center-certified graders using a standardized protocol and then computed in mm 2 . Results While no difference in FD was observed for the entire retina in DR compared to normal controls, a significantly smaller FD was found in the far-periphery of the DR eyes (P Conclusions Peripheral FD on UWF FA is reduced in DR eyes compared to normal eyes and is correlated with the severity of retinal non-perfusion. As FD can be calculated automatically without need for correction of peripheral distortion, it may prove to be a useful surrogate biomarker when precise quantification of non-perfusion is not feasible.