Chapter 6 - Effect of Modifiable Risk Factors on the Incidence and Progression of Diabetic Retinopathy

Abstract

The modifiable risk factors for diabetic retinopathy include glycemic control, hypertension, inhibition of the renin-angiotensin system, serum lipid levels, dietary intake of omega-3 fatty acids, physical activity, sedentary behavior, obesity, aspirin therapy, and smoking. Glycemic control is the most important modifiable risk factor for diabetic retinopathy. An exponential relationship between hemoglobin A1c (HgbA1c) and diabetic retinopathy progression has been demonstrated in multiple clinical trials. A target HgbA1c <7% is associated with a lower incidence and progression of retinopathy. Hypertension is also a primary risk factor due to the microvascular damage that may exacerbate the small vessel injury caused by elevated glucose levels. Blood pressure (BP) control can reduce the risk of retinopathy, but there may be a floor effect for systolic BP less than 120mm Hg. Inhibition of the renin-angiotensin system by angiotensin converting enzyme inhibitors or angiotensin receptor blockers has been shown to reduce the progression of diabetic retinopathy. The reduction of lipid levels can reduce hard exudates and microaneurysms in diabetic retinopathy. In addition, multiple studies demonstrate that obesity increases the risk of retinopathy. There is also evidence that increased physical activity, reduced sedentary behavior, and increased dietary intake of omega-3 fatty acids may reduce retinopathy progression. Aspirin therapy and smoking are not linked to an increased risk of retinopathy. Eye care providers must communicate effectively with the patient's diabetes care team to encourage the management of systemic risk factors that can alter the course of the disease.