Experimental Drug Therapies for the Treatment of Wet-Type Age-Related Macular Degeneration :: Medicine Medical Disease Papers

Experimental Drug Therapies for the Treatment of Wet-Type Age-Related Macular Degeneration In a society where technology has lengthened the average lifespan, age-related disorders present new treatment challenges. In the United States, senior citizens over the age of 65 account for 21% of the population (US, 2001). This group of people will experience changes in their perceptual systems as they age, making it harder for them to function. Some of these changes will occur systematically and naturally, while others will result from disease. In the case of vision, age-related macular degeneration (AMD) is the leading cause of visual impairment in the elderly population (Levin, 1997). Experts estimate that ten million senior citizens over the age of 75 suffer with AMD, approximately one third of Americans 75 and older (Levy, 1999). AMD attacks the retina of aging eyes and is found in two forms. The most common form diagnosed is dry-type AMD. In this disease, accounting for 85% of all AMD diagnoses (Thompson & Daniels, 1998), the layers of the retina deteriorate and thin in the fovea resulting in severe vision loss in the central line of vision. Often, fat deposits, called drucen, develop and further impair vision. Wet-type AMD makes up the remaining 15% of AMD diagnoses and progresses more rapidly and painfully than dry-type AMD. This form of AMD is responsible for severe visual impairment in 90% of all AMD cases diagnosed (Gisele & Bressler, 2001; Thompson & Daniels, 1998). Although dry-type AMD does not usually predict wet-type AMD, between 10-20% of patients with dry-type AMD eventually develop wet-type AMD (Gisele & Bressler, 2001). Wet-type AMD is characterized by choroidal neovascularization (CNV), or the growth of new blood vessels in the layers of the retina (Gisele & Bressler, 2001). Not only do these new capillaries impede vision by blocking incoming light, they also leak blood into the surrounding tissues causing further damage. Currently, the Federal Drug Administration (FDA) has only approved two treatment techniques for wet-type AMD (Yam & Netting, 1999; Visudyne, 2000). Researchers first developed photocoagulation, a procedure utilizing lasers to cauterize new capillaries and seal leaks. Unfortunately, this treatment is only useful in approximately 10% of patients who seek it and, while photocoagulation does decrease vision loss, the results are only short-term and the risk of damage to nearby photoreceptors is high (Gisele & Bressler, 2001; Yam & Netting, 2001; Thompson & Daniels, 1998). The most recently approved treatment option is verteporfin photodynamic therapy, a two-step treatment approved by the FDA in 2000 (Visudyne, 2000).