SANTA CLARA, Calif., April 17 -- The US Food and Drug Administration (FDA) has approved Coherent Inc.'s Opal photoactivator and Visudyne (verteporfin for injection) therapy to treat the wet form of age-related macular degeneration, or AMD. The disease is the leading cause of blindness in the western world in people over the age of 50. According to Coherent, the FDA concluded that Visudyne therapy was most appropriate for patients with predominantly classic subfoveal choroidal neovascularization (CNV). Patients suffering from this form of AMD can lose their ability to read, drive and recognize faces in as little as two months to three years.The FDA application -- filed jointly by Coherent and QLT PhotoTherapeutics Inc. -- covers Coherent's laser, which the company said was developed specifically for use in photodynamic therapy, as well as verteporfin for injection, the drug that is activated by the 689-nm diode laser. CIBA Vision Corp., the eye care unit of Novartis AG, is to market the drug worldwide, while Coherent will handle global marketing of its Opal laser.