Diabetic Retinopathy

Evaluation Of Diabetic Retinopathy

An important cause of blindness, diabetic retinopathy has few visual or ophthalmic symptoms until visual loss develops. At present, laser photocoagulation for diabetic retinopathy is effective at slowing the progression of retinopathy and reducing visual loss, but the treatment usually does not restore lost vision. Because these treatments are aimed at preventing vision loss and retinopathy can be asymptomatic, it is important to identify and treat patients early in the disease. To achieve this goal, patients with diabetes should be routinely evaluated to detect treatable disease.

Dilated indirect ophthalmoscopy coupled with biomicroscopy and seven-standard field stereoscopic 30° fundus photography are both accepted methods for examining diabetic retinopathy. Stereo fundus photography is more sensitive at detecting retinopathy than clinical examination, but clinical examination is superior for detecting retinal thickening from macular edema and for early neovascularization. Fundus photography also requires both a trained photographer and a trained reader.

The use of film and digital nonmydriatic images to examine for diabetic retinopathy has been described. Although they permit undilated photographic retinopathy screening, these techniques have not been fully evaluated. The use of the nonmydriatic camera for follow-up of patients with diabetes in the physician’s office might be considered in situations where dilated eye examination cannot be obtained.

Guidelines for the frequency of dilated eye examinations have been largely based on the severity of the retinopathy^[1,4]. For patients with moderate-to-severe NPDR, frequent eye examinations are necessary to determine when to initiate treatment. However, for patients without retinopathy or with only few microaneurysms, the need for annual dilated eye examinations is not as well defined. For these patients, the annual incidence of progression to either proliferative retinopathy or macular edema is low; therefore, some have suggested a longer interval between examinations^[5]. Recently, analyses suggested that annual examination for some patients with type 2 diabetes may not be cost-effective and that consideration should be given to increasing the screening interval^[6]. However, these analyses may not have completely considered all the factors: 1) The analyses assumed that legal blindness was the only level of visual loss with economic consequences, but other visual function outcomes, such as visual acuity worse than 20/40, are clinically important, occur much more frequently, and have economic consequences. 2) The analyses used NPDR progression figures from newly diagnosed patients with diabetes^[7]. Although rates of progression are stratified by HbA_1c levels, newly diagnosed patients are different from those with the same level of retinopathy and have a longer diabetes duration. While rates of progression correlate with HbA_1c levels, newly diagnosed patients with the same level of retinopathy progress differently than those with longer duration of disease. A person with a longer duration of diabetes is more likely to progress during the next year of observation^[8]. 3) The rates of progression were derived from diabetic individuals of northern European extraction and are not applicable to other ethnic and racial groups who have higher rates of retinopathy progression, such as African- and Hispanic-Americans^[9,10].

In determining the examination interval for an individual patient, the eye care provider should also consider the implications of less frequent eye examinations. Older people are at higher risk for cataract, glaucoma, age-related macular degeneration, and other potentially blinding disorders. Detection of these problems adds value to the examination but is rarely considered in analyses of screening interval. Patient education also occurs during examinations. Patients know the importance of controlling their blood glucose, blood pressure, and serum lipids, and this importance can be reinforced at a time when patients are particularly aware of the implications of vision loss. In addition, long intervals between follow-up visits may lead to difficulties in maintaining contact with patients. Patients may be unlikely to remember that they need an eye examination after several years have passed.

After considering these issues, and in the absence of empirical data showing otherwise, persons with diabetes should have an annual eye examination.

Diabetes Care. 2003;26(1) © 2003 American Diabetes Association, Inc.

Cite this: Diabetic Retinopathy - Medscape - Jan 01, 2003.