Characteristic distribution of microaneurysms and capillary dropouts in diabetic macular edema

Purpose To investigate the distribution pattern of microaneurysms (MAs) and capillary dropouts (CDOs) related to retinal thickness in patients with diabetic macular edema (DME). Methods We designed a cross-sectional observational study in which we manually merged fluorescein angiography and optical coherence tomography (OCT) map and located MAs and CDOs areas. The density of MAs, the width and the length of circumference of CDOs, and the number of MAs adjacent to CDOs were compared between highly thickened (white area (WA) in OCT map) and border areas (red area (RA)). Results We examined 115 eyes of 115 patients with DME. The density of MAs in RA (1.086 +/- 0.616) was significantly higher than that in WA (0.8601 +/- 1.086) (p = 0.002). The MA rates adjacent to CDOs in WA and RA were 79.1% and 80.7%, respectively. In the RA, the size of CDO adjacent to MAs was smaller (p = 0.013), but its circumference was longer (p = 0.018), and the number of MAs adjacent to CDOs was larger than those in WA (p = 0.002). The total length of circumference of CDOs was significantly correlated with the number of MAs adjacent to CDOs in WA (p = 0.011, R-2 = 0.68) and RA (p = 0.008, R-2 = 0.81). Conclusion Smaller but more CDOs with longer circumference adjacent to MAs contribute to the higher density of MAs in the surrounding areas of DME.