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1. DIABETIC RETINOPATHY
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ESSENTIALS OF DIAGNOSIS
By 20 years after diagnosis of diabetes, 99% of patients with type 1 diabetes and 60% of patients with type 2 diabetes will have diabetic retinopathy.
Nonproliferative diabetic retinopathy: can be mild, moderate, or severe. Microvascular changes are limited to the retina.
Proliferative diabetic retinopathy: new blood vessels grow on the surface of the retina, optic nerve, or iris.
Diabetic macular edema: central retinal swelling; can occur with any severity level of diabetic retinopathy; can reduce visual acuity if the foveal center is involved.
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General Considerations
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Diabetic retinopathy is present in about one-third of patients in whom diabetes has been diagnosed, and about one-third of those have sight-threatening disease. In the United States, it affects about 4 million people; it is the leading cause of vision loss worldwide among adults aged 25–74 years; and the number of affected individuals aged 65 years or older is increasing. Worldwide, there are approximately 93 million people with diabetic retinopathy, including 28 million with vision-threatening disease. Retinopathy increases in prevalence and severity with increasing duration and poorer control of diabetes. In type 1 diabetes, retinopathy is not detectable for the first 5 years after diagnosis. In type 2 diabetes, about 20% of patients have retinopathy at diagnosis, likely because they had diabetes for many years before diagnosis. Macular involvement is the most common cause of legal blindness in type 2 diabetes.
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There are two main categories of diabetic retinopathy: nonproliferative and proliferative. Diabetic macular edema can occur at any stage in both nonproliferative and proliferative retinopathy and is the most common reason for ophthalmic diabetic treatment.
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Nonproliferative retinopathy (previously known as “background” retinopathy) is subclassified as mild, moderate, or severe. It represents the earliest stage of retinal involvement by diabetes (eFigure 7–53, eFigure 7–54, eFigure 7–55). During this stage, the retinal capillaries leak proteins, lipids, or red cells into the retina. When this process occurs in the macula and causes clinically significant macular edema, visual acuity is affected; this is the most common cause of visual impairment in patients with type 2 diabetes.
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