Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in people 60 years of age or older in the Western Hemisphere (). There are approx 15 million people affected by AMD in the United States, as AMD affects approx 18% of Americans between the ages of 65 and 74 yr and 30% of those aged 75 yr and older (). The diagnosis of AMD is based on visual dysfunction and characteristic macular findings (). AMD has been classified into neovascular (wet or exudative) and nonneovascular (dry) types. Neovascular AMD is less common but far more devastating than the dry type. The Beaver Dam Study demonstrated a prevalence of neovascular AMD that is approximately one-tenth the prevalence of the dry type (). The most severe form of dry AMD is geographic atrophy, which accounts for 12 to 21% of legal blindness caused by AMD, while the neovascular form accounts for the balance (, , ). Neovascular AMD affects approx 1 million Americans, and each year about 200,000 new cases are diagnosed. Without treatment, most of these patients with neovascular AMD will progress to visual acuity of 20/200 or worse within 2 yr (,). Even though there is clearly an association with advancing age, identifying other factors that put a patient at risk for development and progression of AMD has proven to be a difficult challenge. Several studies have demonstrated an increased risk with cigarette smoking (, , , , , ), and the Rotterdam Study showed a dose—response relationship between smoking and AMD (). There are conflicting reports on the association between AMD and diabetes, cardiovascular disease, hypercholesterolemia, hypertension, alcohol use, obesity, aspirin use, and estrogen use (,). Diet may play a role. The type and amount of dietary fat intake may modify risk of progression of AMD, and intake of fish, fruit, nuts, and green leafy vegetables may be protective (, , ). Antioxidant intake has been proven to be beneficial in certain patients with AMD (). Recently, there has been much interest and investigation into the role of genetic influences on AMD. Studies have demonstrated an increased risk of AMD if a first-degree family member is affected. Approximately 20% of AMD patients have a positive family history, and monozygotic twins demonstrate higher levels of concordance (, , , , , , , ).