Complications of Diabetes Mellitus: Eye Complications

Glaucoma and Cataracts

Glaucoma and cataracts may develop earlier in diabetes patients, compared with those without diabetes (see Glaucoma and Cataract ).

Retinopathy

In diabetes, pathologic changes in the retinal vasculature pose a major long-term threat to vision. In nonproliferative diabetic retinopathy, microaneurysms, small "dot and blot" hemorrhages, hard exudates (lipid material that can be toxic to the retina), and retinal infarcts known as "cotton wool spots" appear. These changes tend to concentrate in the macula, where they can blur and distort central vision.

In proliferative retinopathy (neovascularization), fragile, abnormal vessels grow into the vitreous, presumably in response to ischemia. Vitreous hemorrhage causes symptoms ranging from "floaters" to complete visual obscuration. Ultimately, tractional retinal detachment can result. Retinopathy is not painful. As a result, the condition can progress without its being detected by the patient.

Good blood glucose control, as indicated by a low hemoglobin A1c, can reduce the risk of ophthalmic involvement and slow its progression.^8-12 Similarly, blood pressure control is important, as poorly controlled hypertension increases the severity of retinopathy.^13-15

Risk Factors

• Poor blood glucose control.
• Hypertension.
• Duration of diabetes.
• Smoking.

Diagnosis

Retinopathy can be diagnosed by ophthalmoscopy with dilated pupils.

Use of a fundus lens at the slit lamp allows a stereoscopic view and facilitates diagnosis of macular edema.

In fluorescein angiography, an intravenous injection of fluorescein followed by serial photography of the fundus reveals leakage from microaneurysms, nonperfusion, and other useful information to guide therapy.

Treatment

For proliferative retinopathy, where vitreous hemorrhage appears likely, panretinal laser photocoagulation often stabilizes neovascularization or even causes it to regress.

When diabetic retinopathy causes clinically significant macular edema (defined by severity of leakage and proximity to the central macula), photocoagulation can slow progression.¹⁶ Individual microaneurysms can be obliterated, or a broader grid photocoagulated, if the leakage pattern is diffuse.

Nutritional Considerations

Nutritional interventions that improve control of blood glucose, blood pressure, and lipid concentrations may help prevent or slow ophthalmic complications.

Glaucoma

Most individuals with diabetes are known to be insulin resistant, and evidence indicates that 85% of persons with type 2 diabetes also have the metabolic syndrome.¹⁷ Both of these conditions are associated with elevated intraocular pressure, a well-known risk factor for glaucoma.¹⁸ Control of high blood pressure (a component of the metabolic syndrome) is also important in the care of glaucoma (see Glaucoma ). Dietary treatments that address these underlying conditions have not yet been found to prevent or treat glaucoma.

Cataract

Individuals with diabetes are at increased risk for cataract. However, no controlled clinical trials using nutrition therapies indicate that diet changes reduce this risk among individuals with diabetes. In the general population, a number of dietary factors are associated with lower cataract risk, including maintenance of ideal weight and normal lipid levels; high intake of antioxidant-containing foods; avoidance of alcohol; and avoidance of sources of galactose (ie, dairy products) (see Cataract ).

Retinopathy

Evidence indicates that control of blood glucose,^11,12 blood pressure,¹⁹ and blood cholesterol²⁰ reduces the onset and progression of diabetic retinopathy.A^21,22 A specific diet therapy suitable for prevention of retinopathy has not yet been established. However, evidence from the Diabetes Complications and Control Trial (DCCT) associated diets high in fat and low in fiber with progression of retinopathy,²³ suggesting that low-fat, high-fiber diets diet may have promise for reducing retinopathy risk.