Comparative effectiveness research (CER) has received widespread attention and federal funding because of its potential to inform and improve treatment decisions. Since 2005, patients and their ophthalmologists have faced a dilemma in treating age-related macular degeneration (AMD)—the leading cause of blindness in the United States. Two closely related drugs have produced dramatic improvements in vision; one has been rigorously tested for use in AMD patients, while the other has been rigorously tested for use in cancer patients, but is now widely used to treat AMD. One drug costs 40 times as much as the other. This Issue Brief summarizes a CER study comparing these drugs head-to-head, and provides the most definitive evidence to date about the safety and effectiveness of the two alternatives