Xuxi Zhang

INTRODUCTION Diabetic retinopathy (DR), a microvascular complication of diabetes, is the leading cause of preventable blindness in working age population. 1, 2 It is reported that after 20 years, nearly all patients with type 1 diabetes and more than 60% of those with type 2 diabetes will develop DR. 3 Studies have identified risk factors of DR development and progression, such as duration of diabetes, hyperglycemia/glycated hemoglobin value (HbA1c), hypertension, hyperlipidemia, pregnancy, nephropathy/renal disease, obesity, smoking, moderate alcohol consumption and physical activity. 1, 3 Several intervention studies aiming at identifying the effect of intervention targeting modifiable risk factors of DR among patients with type 2 diabetes have been conducted. However, the results of these trials are not consistent in terms of the effect of interventions on reducing the risk of developing DR and/or its worsening. For instance, with regard to the interventions on hyperglycemia, the Veterans Affairs Diabetes Trial (VADT) found intensive glucose control had no significant effect on preventing DR development but had significant effect on slowing down its worsening 4, 5 , while the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation (ADVANCE) trial found that intensive glucose control had no effect on delaying DR progression (development or worsening). 6 In the meantime, another study conducted in Japan found that intensive glucose control had significant effect on reducing the risk of both development and worsening of DR. 7 With respect to interventions on hypertension, the Appropriate Blood Pressure Control in Diabetes (ABCD) trail 8 found intensive blood pressure control had no effect on preventing DR development, but UK Prospective Diabetes Study (UKPDS) 9, 10 found it to be significantly effective. In addition, some trails have also proven that interventions on multi ‐ factors like blood glucose, blood pressure, dietary, physical activity and smoking were effective. 11 ‐ 13 To date, no study has gathered all the evidence on different kinds of interventions targeting modifiable risk factors of DR and compared their effects to find out how to better perform interventions to prevent and control DR among patients with type 2 diabetes. This study aims to answer the following three questions by carrying out a meta ‐ analysis of randomized control trials (RCTs): First, could interventions targeting modifiable risk factors of DR (blood glucose, blood pressure, lipid, dietary, physical activity and smoking) reduce the risk of developing DR and/or its worsening among patient with type 2 diabetes? Second, among these interventions, what type of intervention is most effective in reducing the risk of developing DR and/or its worsening? 7 163 Prevention and control of diabetic retinopathy