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 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.