AIM: To observe the changes of choroidal thickness(CT)in diabetic patients with different stages of non-proliferative diabetic retinopathy(NPDR)and then investigate the relationship between CT and diabetic retinopathy(DR), to assess the value of enhanced depth imaging optical coherence tomography(EDI-OCT)in the diagnosis of choroidopathy in early-stage DR.

METHODS: A total of 85 eyes of 55 patients with type 2 diabetes mellitus(DM)were included in this study. The patients were divided into three groups according to China Clinical Guidelines of DR in 2014, including non-diabetic retinopathy(NDR)group(28 eyes), mild and moderate NPDR group(27 eyes), and severe NPDR group(30 eyes). The control group included 24 normal subjects(35 eyes). The best corrected visual acuity(BCVA)and CT among normal eyes, and eyes with NDR, mild/moderate NPDR and severe NPDR were compared. Data were analyzed using SPSS 18.0.

RESULTS: Visual changes: The median LogMAR BCVA visions were 0.00 in control group, 0.10 in NDR group, 0.15 in mild and moderate NPDR group and 0.30 in severe NPDR group, the difference between each group was statistically significant(P<0.01). The changes of CT in diabetic patients with different stages of NPDR: CT in the subfoveal area and T1, T3, N1, N3, S1, S3, I1 and I3 sites in the four groups were statistically significant(F=3.975, 3.365, 3.991, 4.290, 6.208, 5.079, 3.234, 2.907, 3.843, P<0.05). CT in the mild and moderate NPDR group decreased and were thinner than the control group, but CT in the severe NPDR group increased significantly.

CONCLUSION: CT in the mild and moderate NPDR group decreased, but it increased significantly in the severe NPDR group, suggesting DM affected not only retina but choroids as well. The study hypothesizes that the changes of CT may played an important role in the progression of DR and the changes of CT had been initiated before DR. This provides significance in the early diagnosis of diabetic choroidopathy.