Data from a wide range of epidemiologic studies, including the Wisconsin Epidemiology Study of Diabetic Retinopathy and the Framingham Eye Study, have demonstrated that diabetes significantly increases the risk of cataract. In diabetic patients under the age of 65, the prevalence of cataract increases 3- to 4-fold compared with demographically similar individuals without diabetes. In those patients over age 65 with diabetes, the prevalence of cataract increases 2-fold compared with demographically similar individuals without the disease.
The Beaver Dam Eye Study evaluated diabetes, cardiovascular disease, selected cardiovascular disease risk factors, and the 5-year incidence of cataract and progressive lens opacification. The investigators found that diabetes was associated with an increased incidence of cortical and posterior subcapsular cataract and with progression of cortical and posterior subcapsular lens opacities.
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Diabetes and Age-Related Macular Degeneration
Data suggest a possible correlation between diabetes and age-related macular degeneration (AMD). In the recent Age-Related Eye Disease Study (AREDS), the dietary glycemic index (dGI) was used to measure the risk of diabetes and cardiovascular disease. A positive correlation was found both between dGI and AMD and between dGI and the severity of AMD. There was a 49% increase in the risk of advanced AMD in subjects with dGI ratings higher than the median for each gender. The investigators concluded that higher glycemic dietary levels increase the risk not only for diabetes and heart disease, but also for AMD.
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Diabetes and Glaucoma
Elevated intraocular pressure, a risk factor for glaucoma, appears to be more common in diabetics. One of the most severe, intractable forms of glaucoma, neovascular glaucoma, is associated with severe proliferative diabetic retinopathy, complicated by rubeosis irides. Certain populations at higher risk for the development of diabetes also show a higher incidence of glaucoma, including African Americans in the United States.
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Diabetes, Medication, and Lifestyle Factors
It is also important to keep in mind that individuals with diabetes are often on multiple medications. These range from antihypertensive and cardiac agents and medications for dyslipidemia to insulin and/or oral hypoglycemic agents. Many of these medications may produce ocular side effects, either alone or in combination, making it important to consider the possibility of a drug complication in the face of any new or unusual visual complaint in the diabetic patient.
A healthy lifestyle—including a well-balanced diet without carbohydrate overload, maintenance of a healthy body mass index, smoking cessation, and normalizing blood pressure and serum lipid profiles—takes on heightened importance in individuals with diabetes and those who are at risk for diabetes, such as those with a family history of diabetes or pre-diabetic symptoms.