Interventions designed to prevent or delay the onset of type 2 diabetes in at-risk patients do not prevent the development of nonproliferative diabetic retinopathy, according to research published in Diabetes Care. However, while the overall prevalence of diabetic retinopathy was not affected in those who took prevention measures, it was lower in patients who never developed diabetes than in those who did.
A Diabetes Prevention Program (DPP) and DPP Outcomes Study (DPPOS) conducted by National Institutes of Health were used to determine the prevalence of diabetic retinopathy in participants who were at risk for developing type 2 diabetes. The DPP created 2 treatment groups. The first group received an intensive lifestyle intervention, and the second was given metformin, (a control group was given a placebo). Participants were followed for up to 5 years. The DPPOS followed participants for up to 20 years following the DPP study, documenting type 2 diabetes outcomes.
The current study used participants from the DPP and DPPOS to conduct 7-field stereo fundus imaging on all willing participants (regardless of diabetes status), which were then graded by the Early Treatment Diabetic Retinopathy Study (ETDRS) grading system and used to diagnose diabetic retinopathy and clinically significant macular edema (CSME). Fundus imaging was completed in years 1, 5, 11, and 16 of the DPPOS. Microaneurysm, exudate, or hemorrhage lesions or an ETDRS grade of 20 or higher was required for a diabetic retinopathy diagnosis. Other demographic and health information was collected by DPP and DPPOS and used to determine risk factors for retinopathy in the current study.
A total of 2499 participants were recruited and 899 (34%), 2128 (84%), 2086 (92%), and 1563 (76%) participants had fundus imaging completed at years 1, 5, 11, and 16, respectively. The prevalence of diabetic retinopathy at years 1, 5, 11, and 16 was 99 of 899 (11.0%), 206 of 2128 (9.7%), 238 of 2086 (11.4%), and 145 of 1563 (9.3%), respectively.
Researchers report no significant difference in prevalence of diabetic retinopathy based on diabetic status or intervention type and no differences were found within treatment groups based on age, sex, race/ethnicity, and BMI.
The results of the current study show that interventions proven to delay or prevent type 2 diabetes in at risk populations has no effect on the development of diabetic retinopathy. Researchers suggest diabetic retinopathy begins developing when a person is prediabetic or overweight/obese due to dysglycemia but propose that prediabetic retinal screening may be unnecessary due to its limited long-term effects on vision.
This study is limited by its short follow-up after diagnosis (while the study lasted for 20 years, it began with patients in the prediabetic phase), its sole use of seven-filed retinal photographs, the 5-year gap between retinal photography preventing the identification of exact onset of retinopathy, missing ophthalmologic evaluation at baseline, and the loss of participants over time throughout the study for various reasons.
White NH, Pan Q, Knowler WC, et al. The effect of interventions to prevent type 2 diabetes on the development of diabetic retinopathy: the DPP/DPPOS experience. Diabetes Care. 2022;45(7):1640–1646. doi:10.2337/dc21-2417