METHODS: A retrospective cross-sectional study was performed at Beijing Friendship Hospital. Enhanced depth imaging spectral-domain optical coherence tomography(EDI-OCT)scans of 68 eyes of 68 type 2 diabetes who with diabetic retinopathy were compared with those of right eyes of 34 age- and gender-matched healthy controls. The choroidal images were binarized into luminal areas(LA)and stromal areas(SA). CVI was defined as the ratio of LA to total circumscribed subfoveal choroidal area. Mean choroidal thickness, mean retinal thickness and mean CVI between patients and controls were compared using t-test.

RESULTS: There were no significant differences in total circumscribed subfoveal choroidal area(0.53±0.14mm2 vs 0.49±0.15mm2), LA(0.35±0.09mm2 vs 0.32±0.10mm2), SA(0.17±0.05mm2 vs 0.17±0.06mm2), or subfoveal choroidal thickness(347.9±76.9μm vs 325.9±92.9μm)between patients with DR and controls(P>0.05). However, there was a significantly lower CVI in patients with diabetes as compared to controls(64.33%±3.25% vs 67.04%±2.46%, P<0.001). The critical value was 63.59%.

CONCLUSION: CVI is a kind of biological indicators which can directly reflect the changes of choroidal internal structure, and it is more stable and reliable than SFCT. For type 2 diabetic patients who with diabetic retinopathy, CVI is lower than that of healthy people.