Wang H, et al. - In this observational cross-sectional study, researchers examined the choroidal thickness and choroidal vascular density parameters and their association with severity of diabetic retinopathy (DR) in patients with diabetes mellitus (DM). One hundred four eyes were included in this study. Compared with normal controls, the eyes of patients with DM exhibited the ratio of the luminal to the choroidal area (L/C ratio) decreased. The subfoveal choroidal thickness increased, but the L/C ratio decreased significantly compared with the DM and normal eyes with the severity of DR eyes. Changes in the L/C ratio can predict the development of DR before clinically evident otherwise. The choroidal deficit in blood flow may be an early pathological change in DR.