2008 Clinical Practice Guidelines - Canadian Diabetes Association

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2008 CLINICAL PRACTICE GUIDELINES S134 Retinopathy Canadian Diabetes Association Clinical Practice Guidelines Expert Committee The initial draft of this chapter was prepared by Shelley R. Boyd MD FRCSC DABO and Filiberto Altomare MD FRCSC KEY MESSAGES • Screening is important for early detection of treatable disease. Screening intervals for diabetic retinopathy vary according to the individual’s age and type of diabetes. • Tight glycemic control reduces the onset and progression of sight-threatening diabetic retinopathy. • Laser therapy reduces the risk of significant visual loss. INTRODUCTION Diabetic retinopathy is the most common cause of new cases of legal blindness in people of working age (1). The Eye Diseases Prevalence Research Group determined the crude prevalence rate of retinopathy in the adult diabetic population of the United States to be 40.3%; sight-threatening retinopathy occurred at a rate of 8.2% (2). Previous data showed the prevalence rate of proliferative retinopathy to be 23% in people with type 1 diabetes, 14% in people with type 2 diabetes and on insulin therapy, and 3% in people receiving oral antihyperglycemic therapies (3). Macular edema occurs in 11, 15 and 4% of these groups, respectively (4). First Nations populations in Canada have high rates of diabetes and its complications (5,6). It is estimated that approximately 2 million individuals in Canada (i.e. almost all people with diagnosed diabetes) have some form of diabetic retinopathy (7). Visual loss is associated with significant morbidity, including increased falls, hip fractures and a 4-fold increase in mortality (8). Among individuals with type 1 diabetes, limb amputation and visual loss due to diabetic retinopathy are the 2 independent predictors of early death (9). DEFINITION AND PATHOGENESIS Diabetic retinopathy is clinically exclusively defined, diagnosed and treated based on the extent of retinal vascular disease. Three distinct forms of diabetic retinopathy are described: 1) macular edema, which includes diffuse or focal vascular leakage at the macula; 2) progressive accumulation of blood vessel change that includes microaneurysms, intraretinal hemorrhage, vascular tortuosity and vascular malformation (together known as nonproliferative diabetic retinopathy) that ultimately leads to abnormal vessel growth (proliferative diabetic retinopathy); and 3) retinal capillary closure, a form of vascular change detected by fluorescein angiography, which is also well recognized as a potentially blinding complication of diabetes, but currently has no treatment options. SCREENING AND DIAGNOSIS Since laser therapy for sight-threatening diabetic retinopathy reduces the risk of blindness (10-13), ophthalmic screening strategies are intended to detect treatable disease. Sightthreatening diabetic retinopathy includes severe nonproliferative diabetic retinopathy, proliferative diabetic retinopathy or clinically significant macular edema. Screening programs consider the differences in incidence and prevalence of retinopathy observed in type 1 and type 2 diabetes, and distinguish between children and adults (see Table 1) (14-19). Diabetic retinopathy rarely develops in children with type 1 diabetes
erative retinopathy was 2%, and none had sight-threatening diabetic retinopathy (11,18,20). However, the prevalence rate increases sharply after 5 years’ duration of diabetes in postpubertal individuals with type 1 diabetes (18). In the Wisconsin Epidemiology Study of Diabetic Retinopathy 4year incidence study, no person
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2008 Clinical Practice Guidelines - Canadian Diabetes Association

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