Diabetes can lead to multiple eye pathologies, including retinopathy, certain lens opacities, increased intraocular pressure, rubeosis iridis, and possibly open-angle glaucoma (91). The association between diabetes and open-angle glaucoma is controversial, with several studies demonstrating an association but several other large studies failing to demonstrate any association (92).
Retinopathy affects more than 300,000 people in the U.S. (90). It is the leading cause of blindness in people age 20 to 64 years old (13). It accounts for 12 percent of all new cases of blindness, with 12,000 to 24,000 new cases each year in the U.S. (13). The prevalence of diabetic retinopathy is 46 percent higher in non-Hispanic blacks and 84 percent higher in Mexican Americans compared to non-Hispanic Caucasians (93). There is evidence to suggest that retinopathy begins to develop at least seven years before type 2 diabetes is clinically diagnosed (94, 95). The Wisconsin Epidemiologic Study of Diabetic Retinopathy examined the prevalence and incidence of diabetic retinopathy (91). The pathogenesis of retinopathy is thought to begin with hyperglycemia, which leads to increased levels of protein kinase C and aldose reductase activities, nonenzymatic glycosylation, vasoactive substances, growth factors, and free radicals (90, 96). These changes cause functional changes, such as increased vitreous fluorometry and abnormal electrical conductance (90). They also cause anatomic changes (90). Glycemic control, as measured by glyco-sylated hemoglobin, and not C-peptide secretion or the type of diabetes, seems to be the most important predictor of diabetic complications, such as retinopathy (8, 96-98). Retinopathy incidence increases above a fasting plasma glucose of > 126 mg/dl (96, 99). The Wisconsin Epidemiologic Study of Diabetic Retinopathy, which studied > 900 patients aged < 30 at onset of diabetes, showed 20 percent of patients at age 15 were affected by retinopathy, 60 percent at age 20, and 80 percent at age 30 (90). The risk of retinopathy increased 50 percent for every 1 percent increase in HbA1c, for every 10-mm Hg increase in systolic blood pressure, and for every three years' diabetes duration (90). The findings in the Wisconsin Epidemiologic Study of Diabetic Retinopathy were similiar to those found in the concurrently run Diabetes Control and Complications Trial (98). A population-based cohort study showed a modest increased risk of incidence of diabetic retinopathy in patients with younger-onset diabetes and hypertension (10 years after the baseline examination) [OR, 1.27; 95 percent CI, 1.03-1.57] (100). There was no consistent association of blood pressure and retinopathy in subjects with older-onset diabetes (100).
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Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...