Progression of diabetic macular edema: Correlation with blood-retinal barrier permeability, retinal thickness, and retinal vessel diameter

PURPOSE. To study the progression of diabetic macular edema (DME) in relation to baseline retinal thickness, retinal vascular leakage, and retinal trunk vessel diameters. METHODS. In this single-center study, 45 patients were enrolled with 62 eligible eyes defined as having DME of a grade less than clinically significant macular edema (CSME). From the start, the patients were included in a multicenter study exploring the effect of ruboxistaurin versus placebo for 3.4 years. Subsequently, the patients were followed up for a mean of 5.7 years by optical coherence tomography, fundus photography, and vitreous fluorometry. Baseline values in eyes that progressed to photocoagulation treatment were compared with values from eyes that did not reach this endpoint. RESULTS. In the 22 eyes of 18 patients in which CSME was diagnosed and treated, mean retinal vascular leakage at baseline was 5.6 (95% CI 4.2-7.6) nm/s, whereas eyes that did not progress to photocoagulation had a significantly lower mean leakage at baseline of 3.4 ( 95% CI 2.7-4.3) nm/s. No significant difference was found for measures of baseline retinal thickness or summarized retinal trunk vessel diameters. Eyes that progressed to photocoagulation treatment ( mean delay to treatment, 3.6 years) had significantly higher foveal thicknesses than did nonprogressing eyes, from 18 months after study initiation. CONCLUSIONS. Progression to photocoagulation treatment for CSME was associated with higher retinal vascular leakage at baseline, whereas baseline retinal vessel diameters and retinal thickness were comparable in progressing and nonprogressing eyes. Baseline leakage was the strongest predictor of progression from non-CSME to photocoagulation for CSME.