Diabetic retinopathy: Screening
- David K McCulloch, MD
David K McCulloch, MD
- Clinical Professor of Medicine
- University of Washington
- Section Editors
- David M Nathan, MD
David M Nathan, MD
- Editor-in-Chief — Endocrinology
- Section Editor — Diabetes Mellitus
- Professor of Medicine
- Harvard Medical School
- Jonathan Trobe, MD
Jonathan Trobe, MD
- Section Editor — Ophthalmology
- Professor of Ophthalmology and Visual Sciences
- Professor of Neurology
- University of Michigan Kellogg Eye Center
Retinopathy is a major cause of morbidity in patients with diabetes . The vast majority of patients who develop diabetic retinopathy (DR) have no symptoms until the very late stages (by which time it may be too late for effective treatment). Because the rate of progression may be rapid and therapy can be beneficial for both symptom amelioration and reduction in the rate of disease progression, it is important to screen patients with diabetes regularly for the development of retinal disease.
Issues related to screening for DR will be reviewed here. The pathogenesis, clinical findings, natural history, and treatment of this disorder are discussed separately. (See "Diabetic retinopathy: Pathogenesis" and "Diabetic retinopathy: Classification and clinical features" and "Diabetic retinopathy: Prevention and treatment".)
RATIONALE FOR SCREENING
Screening for DR is important because the majority of patients who develop DR have no symptoms until macular edema (ME) and/or proliferative diabetic retinopathy (PDR) are already present. In addition, the efficacy of laser photocoagulation in preventing visual loss from PDR and ME is well established in randomized trials (see "Diabetic retinopathy: Prevention and treatment", section on 'Panretinal photocoagulation' and "Diabetic retinopathy: Prevention and treatment", section on 'Focal laser photocoagulation'). However, laser therapy is more beneficial in preventing visual loss than reversing diminished visual acuity. Thus, early detection through screening programs and appropriate referral for therapy are important to preserve vision in individuals with diabetes.
METHOD OF SCREENING
For the initial screening examination, we prefer evaluation by an ophthalmologist or optometrist who is experienced with diagnosing and treating DR. In certain settings (eg, when previous exams have been normal or when there is a shortage of eye care specialists), subsequent examinations can be done with retinal photographs if there is a trained photographer and reader. A comprehensive exam is required for follow-up of abnormalities detected on retinal photographs. These recommendations are consistent with American Diabetes Association (ADA) guidelines .
Ophthalmoscopy is a reasonable screening method when performed by well-trained personnel on dilated fundi. The accuracy of ophthalmoscopy is substantially lower when performed by primary care physicians . As an alternative, seven-field stereoscopic fundus photography is another acceptable method but also requires both a trained photographer and a trained reader. Fundal photography compares favorably with ophthalmoscopy (performed by an experienced ophthalmologist, optometrist, and ophthalmic technician) . In one study of 1949 patients participating in the Wisconsin Epidemiology Study of Diabetic Retinopathy (WESDR), there was almost complete agreement between ophthalmoscopy and the results of fundus photography in 86 percent of cases, with no significant interobserver differences. Of note, the center that conducted the study is an academic center that focuses on diabetic retinopathy. Whether these results are generalizable is unknown.
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