Purpose To study the relationship between the location of cystoid spaces and retinal capillary nonperfusion areas in diabetic cystoid macular edema (DCME). Methods In this retrospective study, 24 eyes of 21 patients with chronic DCME were followed using optical coherence tomography angiography. The capillary density of the superficial capillary plexus and deep capillary plexus was measured using AngioAnalytics software in all DCME eyes and in 20 healthy controls. Diabetic cystoid macular edema improved spontaneously or after treatment in 11 eyes. Results The intraretinal cystoid spaces were surrounded by capillary-flow void areas in the superficial capillary plexus in 71% of cases and in the deep capillary plexus in 96% of cases. The deep capillary plexus had lost its regular pattern in all cases. The capillary density was decreased in both plexus (mean decrease of -23.0% in the superficial capillary plexus and -12.4% in the deep capillary plexus vs. normal). In the 11 cases with DCME resolution, the capillary did not reperfuse in areas of resolved cystoid spaces, and the capillary density did not change significantly. Conclusion In chronic DCME, cystoid spaces were located within capillary dropout areas. No reperfusion occurred after DCME resolution. The impact of the severity of this nonperfusion on the risk of recurrence of DCME remains to be clarified.
