Changes in the choroid detected by ultrawide-field optical coherence tomography angiography in type 2 diabetes mellitus patients without diabetic retinopathy

Aim: The study objective was to investigate the choroidal changes in type 2 diabetes mellitus (T2DM) patients without diabetic retinopathy (DR). Methods: This was a cross-sectional study. Controls without diabetes and T2DM patients without DR (NDR) were included. Ultrawide-field (24 x 20 mm2) optical coherence tomography angiography (OCTA) was performed to analyse choroidal thickness and vessel density. All OCTA images were divided into 3 x 3 grids. The grid centre was considered the central area, while the rest was defined as the peripheral area. Results: No differences between groups were observed in the flow density of the choriocapillaris (CC), choroidal thickness (ChT) and choroidal vascular index (CVI) of the large and medium choroidal vessel (LMCV) in the central area. In the eight peripheral areas, the mean flow density of the CC did not differ between the groups, while the mean CVI and ChT were decreased in the NDR group (P< 0.05). In each peripheral area, the mean CVI and ChT were decreased in the NDR group (P< 0.05, except in the infratemporal area and nasal area for ChT and in the infratemporal area for CVI). In the correlation analysis, both mean peripheral CVI and ChT correlated with age and the duration of diabetes. Conclusion: Early choroidal lesions tended to be peripheral in the LMCV in patients with diabetes without DR and correlated with age and the duration of diabetes.