Symmetry of peripheral retinal nonperfusion in diabetic retinopathy by ischemic index

PURPOSE: Diabetic retinopathy is the leading cause of blindness among working-age adults in most developed countries. It affects eyes bilaterally and is generally believed to be symmetrical, yet there are few studies evaluating the symmetry of diabetic retinopathy. The purpose of the present study was to evaluate the symmetry of the amount of peripheral retinal ischemia in patients with diabetic retinopathy. METHODS: Ultra-widefield fluorescein angiography images were obtained on both eyes of 54 subjects, mean age 56.4 years, from an urban eye clinic. A single, high quality image from the arteriovenous phase of the angiogram of each eye was selected for analysis. The total area of gradable fundus and area of nonperfusion seen in the arteriovenous phase of the ultra-widefield fluorescein angiogram were determined. An ischemic index (ISI) was calculated by dividing the non-perfused retinal area by the total retinal area and multiplying by 100. RESULTS: The mean ISI OD was 11.27, mean ISI OS was 11.64. The mean absolute value (±SD) of ISI difference between OD and OS was 4.46 ± 6.09. A difference in ISI of 10% or less was found in 92.6% of subjects. A statistically significant correlation was found in the ISI between right and left eyes (r(s) = 0.80, p < 0.0001) and there was no statistically significant difference in ISI between the right and left eyes (p = 0.85). CONCLUSION: Asymmetrical retinopathy in diabetic patients is uncommon and additional pathological processes should be considered in the presence of asymmetric DR.