Many risk factors were proved to be related to the progression of PDR, such as duration of diabetes, poor glycaemic control and uncontrolled hypertension.[29] Certain cytokines and growth factors were also considered to be correlated with the severity of PDR, including angiotensin II.[10] In this study, we excluded patients using ACEI or ARB to exclude the influence of it may bring to this study. This evidence concerns the gene AGT and diabetes mellitus.