Ethnic Differences in the Prevalence of Diabetic Retinopathy in Persons With Diabetes When First Presenting at a Diabetes Clinic in South Africa

OBJECTIVE: To describe the prevalence and associated risk factors for diabetic retinopathy (DR) within a multiethnic population at presentation to a diabetes clinic in South Africa. RESEARCH DESIGN AND METHODS: Retinal photography was conducted using a nonmydriatic digital camera without mydriasis and graded by one of three senior graders. Logistic regression analyses were used to assess the association between any DR, referable DR, and clinical risk factors. RESULTS: A total of 1,537 persons with type 1 and 3,978 with type 2 diabetes were included. Prevalence of any DR in type 1 diabetes was 35.2% (background DR 26% and referable DR 9.2%) and in type 2 diabetes was 20.5% (14.1 and 6.4%, respectively). In type 1 diabetes, there was an increased risk of any DR in Asian Indians, whereas the risk of referable DR was increased for indigenous Africans compared with Caucasians. In type 2 diabetes, the risk was increased for all non-Caucasians compared with Caucasians. Longer duration of diabetes and elevated HbA(1c) were independently associated with any and referable DR in both type 1 and type 2 diabetes, with the addition of hypertension and smoking in type 1 diabetes when adjusted for age at diagnosis of diabetes, sex, and ethnicity. CONCLUSIONS: The prevalence of DR in this population from South Africa was similar to that reported globally; however, ethnic differences were observed. Increasing duration of diabetes and poor glycemic control were the strongest risk factors associated with any and referable DR in both type 1 and type 2 diabetes.