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 broadly classified as nonproliferative, which is subclassified as mild, moderate, or severe, or proliferative, which is less common but causes more severe visual loss. 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, retinopathy is present in about 20% of patients at diagnosis and may be the presenting feature.
Clinical assessment comprises visual acuity testing, stereoscopic examination of the retina, retinal imaging with optical coherence tomography, and sometimes fluorescein angiography.
Nonproliferative retinopathy manifests as microaneurysms, retinal hemorrhages, venous beading, retinal edema, and hard exudates (eFigure 7–51) (eFigure 7–52) (eFigure 7–53) (eFigure 7–54). In mild nonproliferative diabetic retinopathy, there are mild retinal abnormalities without visual loss. Reduction of vision is most commonly due to diabetic macular edema, which may be focal or diffuse, but it can also be due to macular ischemia (eFigure 7–55). Macular involvement is the most common cause of legal blindness in type 2 diabetes. Macular edema may be associated with treatment with thiazolidinediones (glitazones).
Moderate nonproliferative diabetic retinopathy with multiple microaneurysms and hemorrhages, mild macular hard exudates, and two cotton-wool spots in the superior retina. (Reproduced, with permission, from Riordan-Eva P, Augsburger JJ. Vaughan & Asbury’s General Ophthalmology, 19th ed. McGraw-Hill, 2018.)
Ultra-widefield (Optomap) image of mild nonproliferative diabetic retinopathy. (Used, with permission, from J Sherman and Optos plc.)