ESSENTIALS OF DIAGNOSIS
Present in ~33% of all diagnosed diabetic patients.
Present in ~20% of type 2 diabetic patients at time of diagnosis of diabetes.
By 20 years after diagnosis of diabetes, 99% of type 1 diabetic patients and 60% of type 2 diabetic patients 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; reduces visual acuity if center involved.
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 new blindness among adults aged 20–65 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 an extensive period of time before diagnosis. Macular involvement is the most common cause of legal blindness in type 2 diabetes.
There are two main categories of diabetic retinopathy: nonproliferative and proliferative. Diabetic macular edema can occur at any stage. Nonproliferative retinopathy is subclassified as mild, moderate, or severe; proliferative retinopathy is less common but causes more severe visual loss.
Nonproliferative (“background”) retinopathy represents the earliest stage of retinal involvement by diabetes (eFigure 7–54, eFigure 7–55, eFigure7–56). During this stage, the retinal capillaries leak proteins, lipids, or red cells into the retina. When this process occurs in the macula (clinically significant macular edema), the area of greatest concentration of visual cells, there is interference with visual acuity; this is the most common cause of visual impairment in patients with type 2 diabetes.
Moderate nonproliferative diabetic retinopathy with multiple microaneurysms and hemorrhages (red arrow), mild macular hard exudates (yellow arrow), and two cotton-wool spots in the superior retina (black arrows). (Reproduced, with permission, from Riordan-Eva P, Augsburger JJ. Vaughan & Asbury's General Ophthalmology, 19th ed. McGraw-Hill, 2018.)
Nonproliferative diabetic retinopathy with hard exudates indicative of macular edema extending into the central macula. (From Victor Chong. Reproduced, with permission, from Riordan-Eva P, Augsburger JJ. Vaughan & Asbury's General Ophthalmology, 19th ed. McGraw-Hill, 2018.)