Purpose: To assess the prevalence of diabetic retinopathy (DR) in type 2 diabetic subjects in urban India using four-field stereo color photography.
Methods: The Chennai Urban Rural Epidemiology Study (CURES) is a population-based study conducted on a representative population of Chennai (formerly Madras) city in South India. Individuals > or =20 years in age (n = 26,001) were screened for diabetes. Of the 1529 known diabetic subjects, 1382 (90.4%) participated in the study. Subjects with newly detected diabetes (n = 354) by the oral glucose tolerance test (OGTT) also consented to participate in the study. All the subjects underwent four-field stereo color photography, and retinopathy was graded in the color fundus photographs according to Early Treatment Diabetic Retinopathy Study (ETDRS) criteria.
Results: The overall prevalence of DR in the population was 17.6% (95% confidence interval [CI]: 15.8-19.5), which included 20.8% (95% CI: 18.7-23.1) in known diabetic subjects and 5.1% (95% CI: 3.1-8.0) in subjects with newly detected diabetes. The prevalence of DR was significantly higher in men than in women (21.3% vs. 14.6%; P < 0.0001) and among subjects with proteinuria (P = 0.002). Logistic regression analysis showed that for every 5-year increase in the duration of diabetes, the risk for DR increased 1.89-fold (95% CI: 1.679-2.135; P < 0.0001). For every 2% elevation of glycated hemoglobin (HbA1c), the risk for DR increased by a factor of 1.7 (95% CI: 1.545-1.980; P < 0.0001).
Conclusions: This study shows that the prevalence of diabetic retinopathy is lower in urban South Indians than in other ethnic groups. However, due to the large number of diabetic subjects, DR is likely to pose a public health burden in India; hence, routine retinal examination is mandatory to detect DR in the early stages.