Decreasing the Risk of Diabetic Retinopathy in a Type 2 Diabetes Study: Part 3

This report is the first evidence that intensive case management reduces risk of new-onset retinopathy in people with established type 2 diabetes. The U.K. Prospective Diabetes Study first demonstrated the effects of improved glycemic control on retinopathy in type 2 diabetes, but the subjects who participated in that landmark study were all newly diagnosed, whereas the patients without retinopathy in this study had a mean duration of diabetes of 7.5 years by the time the case management intervention was begun. Although the number of subjects with established retinopathy in this study was not sufficient to draw conclusions about progression of retinopathy compared with those who had none at baseline, the response observed in the latter suggests that early intervention with case management is an effective approach to reducing the burden of retinopathy in patients with type 2 diabetes. This conclusion is reinforced by the finding that even when case management is maintained for a short duration (mean <2 years), it is sufficient to diminish the risk of retinopathy.

The mechanisms for the effect of case management on reduction in the development of new-onset retinopathy may be related to any of the different facets of the case management process, although the major factor is likely to be improved glycemic control. Although A1C concentrations were not consistently evaluated at the time the follow-up photographs were taken, in the main trial the case management group showed a persistent improvement in the A1C that was greater than in the standard care group (6), suggesting that the decreased risk of retinopathy is likely due to improvement in glycemia. This study, therefore, confirms the necessity of providing adequate education and follow-up support, as delivered in this trial that utilized case management and frequent intervention, in order to achieve and maintain an A1C improvement over and above the standard care given to this county clinic Medi-Cal population.

However, other elements of the case management approach may well have contributed to the reduction in development of new-onset retinopathy. With adequate surveillance and support, glycemia improves, but, as demonstrated in our primary report, this improvement was associated with significant decreases from baseline to end of study in diastolic blood pressure, LDL cholesterol, and total cholesterol and an increase in HDL cholesterol in the intervention group. Thus, case management not only resulted in improvement of glycemic control but also had an effect on diminishing the risk of microvascular disease, as measured by retinopathy.