Simplified Correction of Ischemic Index in Diabetic Retinopathy Evaluated by Ultra-widefield Fluorescein Angiography

Purpose: To develop a novel, simplified method for correcting the ischemic index of nonperfused areas in diabetic retinopathy (DR). Methods: We performed a retrospective review of 103 eyes with naive DR that underwent ultra-widefield angiography (UWFA) over a year. UWFAs were graded according to the quantity of retinal non-perfusion, and uncorrected ischemic index (UII) and corrected ischemic index (CII) were calculated using a simplified, novel method. Results: The average differences between UII and CII in the non-proliferative DR group and the proliferative DR group were 0.7 ± 0.9% in the <25% CII group, 3.0 ± 0.9% in the 25% to 49.9% CII group, and 3.6 ± 0.6% in the>50% CII group, respectively. A CII >25% was critical for determining DR progression (p < 0.001). Conclusions: Distortion created by UWFA needs to be corrected because the difference between UII and CII in DR increases with the ischemic index.