Age-related macular degeneration (AMD) is the leading cause of severe vision loss in older Americans. AMD is a degenerative disease that affects the macula, or the central part of the retina, which has the highest density of photoreceptors, allowing for high-resolution central visual acuity. An estimated 1.75 million persons in the United States were diagnosed with AMD in 2000, an incidence that is expected to increase to nearly 3 million by 2020.
There are two major forms of AMD: nonexudative (“dry”) and exudative or neovascular (“wet”). Nonexudative AMD accounts for 85%-90% of all cases and neovascular AMD the remaining 10%-15%; however, the latter form is responsible for more than 80% of cases of severe vision loss or legal blindness (ie, visual acuity of 20/200 or worse) resulting from AMD. The main cause of vision loss in wet AMD is the development of choroidal neovascularization (CNV), which has been shown to occur in 18% of patients over 5 years.