Pharmacologic Treatment in Diabetic Macular Edema

Department of Ophthalmology and Visual Science, Kentucky Clinic, Lexington, Kentucky, U.S.A. 

Diabetes mellitus is a group of metabolic diseases characterized by an increased blood glucose level secondary to defects in insulin secretion and/or action. According to the American Diabetes Association, as of 2002, the United States diabetes prevalence is 18.2 million people (6.3% of the population). Diabetics suffer from acute complications of the disease such as diabetic ketoacidosis and hyperosmolar nonketotic syndrome as well as chronic complications ranging from microvascular disease (nephropathy, neuropathy, retinopathy) to macrovascular disease (1). 

Diabetic retinopathy is the leading cause of blindness in people aged 20-74 years in the United States and causes from 12,000 to 24,000 new cases of blindness each year. Manifestations of diabetic retinopathy include retinal microaneurysms, hemorrhages, hard exudates, cotton-wool spots, microvascular abnormalities, growth of abnormal blood vessels and fibrous tissue, and macular edema (2). It was estimated that of the 7.8 million patients affected with diabetes in 1993, 95,000 are expected to develop macular edema each year (3). 

Currently, there are three main pharmacologic approaches to the treatment of DME in practice or under study steroids (the intravitreal injection of triamcinolone acetonide, fluocinolone acetonide sustained drug delivery implant, dexamethasone biodegradable implant), PKC inhibitors, and VEGF inhibitors. 

Corticosteroids have been used to treat a variety of ocular diseases. Traditionally, delivery of corticosteroids for posterior-segment eye diseases has been achieved through oral systemic therapy and periocular injections. Oral corticosteroids have not been widely used to treat DME, but when used for posterior inflammatory uveitis, they require high concentrations to reach therapeutic levels in the posterior segment. These high doses often result in systemic side effects (24). Periocular corticosteroid administration often must be repeated and may be associated with complications such as ptosis and inadvertent needle penetration of the globe. 

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