SANTA CLARA, Calif., Feb. 16 -- Coherent Inc. has received an approvable letter from the US Food and Drug Administration (FDA) for the Opal Photoactivator and Visudyne (Verteporfin for injection) therapy to treat the wet form of age-related macular degeneration (AMD). The disease is the leading cause of blindness in people over the age of 50 in the western world. According to Coherent, the FDA has indicated that it will, following final review, approve the Opal Photoactivator, having concluded that Visudyne therapy is most appropriate for patients with the wet form of AMD, which is characterized by the presence of predominantly classic subfoveal choroidal neovascularization. This was the indication sought in the joint drug/device submission.The FDA application for Visudyne therapy was filed jointly by Coherent and QLT PhotoTherapeutics Inc.; it covers Coherent's new Opal Photoactivator laser -- which the company said was developed specifically for use in photodynamic therapy -- and Verteporfin for injection, the drug that is activated by the special purpose 689-nm diode laser. Upon commercialization, the drug will be marketed worldwide by CIBA Vision Corp., the eye care unit of Novartis AG. Coherent will handle worldwide marketing of the Opal laser.