Retinal neovascularization of diabetic retinopathy might be associated with genetic risk factors and environmental risk factors.

Inclusion Criteria:

• T2DM was diagnosed according to the World Health Organization Expert Consultation Report 1999 and consisted of one of the following: fasting blood glucose (FBG) ≥7.0 mmol/L (≥126 mg/dL), blood glucose ≥11.1 mmol/L (≥200 mg/dL) 2 hours after an oral glucose tolerance test (OGTT); or a random blood glucose ≥11.1 mmol/L (≥200 mg/dL).
• DR was clinically graded in accordance with the International Clinical Diabetic Retinopathy guidelines based on fundus fluorescence angiography.
• All participants with PDR underwent a comprehensive dilated fundus examination to detect DR by indirect ophthalmoscopy and were diagnosed by fundus fluorescence angiography.

Exclusion Criteria:

• Patients were excluded if they had acute complications of diabetes mellitus, type 1 diabetes mellitus, other types of diabetes, serious cardiovascular, hepatic, nephritic or other complications, other serious primary diseases or mental illness.