DUBLIN, Calif., June 19 -- More than 500 Visulas 690s lasers have been sold since the US Food and Drug Administration (FDA) allowed the use of the laser in the activation of Visudyne, the therapy used to treat the wet form of age-related macular degeneration (AMD), Zeiss Humphrey Systems said. Visudyne therapy is used for the treatment of AMD patients with predominantly classic subfoveal choroidal neovascularization. Only 10-15 percent of the estimated 500,000 people who get wet AMD every year are eligible for existing treatments. Medical experts estimate between 40-60 percent of all wet AMD cases will form predominantly classic lesions as the disease progresses; these lesions can cause blindness.