Correlation of Diabetic Retinopathy Ischemic Index and Diabetic Macular Edema

Abstract

Purpose: : To correlate the ischemic index of diabetic retinopathy (DR) with the amount of macular edema (ME) measured by OCT and to assess the impact of Pegaptanib (Macugen) or panretinal photocoagulation (PRP) for proliferative diabetic retinopathy (PDR) on ME at 6 weeks.

Methods: : This study was a retrospective analysis of 15 subjects randomized to receive Pegaptanib or PRP for PDR in the affected eye. The ischemic index (II) was formulated to quantify the amount of ischemia noted on fluoroscein angiogram (FA), particularly by evaluating for the presence or absence of capillary non-perfusion (CNP), microaneurysms, and dye leakage. Each of the above was graded from 0% (no quadrants involved) to 100% (4 quadrant involvement), and the percentages were added together to provide a number ranging from 0 to 300. Subjects with an II from 0 to 99 were defined as mild, from 100 to 199 were moderate, and those from 200 to 300 were defined as severe. In total, 8 eyes received Pegaptanib and 7 received PRP. The amount of ME was measured at baseline and then at 6 weeks.

Results: : Nine eyes showed severe II and had a baseline macular thickness of 165 microns. 6 eyes showed moderate II and had a baseline macular thickness of 216 microns. After treatment with Pegaptanib, OCT thickness at 6 weeks showed an average decrease of 24 microns. After treatment with PRP, OCT thickness was increased by 26 microns.

Conclusions: : The II does not correlate with the ME measured by OCT. The group of eyes randomized to Pegaptanib injection showed a significant reduction in OCT thickness from baseline compared to the ones randomized to PRP. The PRP group had an increase in the OCT thickness at 6 weeks.

Keywords: diabetic retinopathy • edema