Mechanisms of action of photodynamic therapy with verteporfin for the treatment of age-related macular degeneration

Age-related macular degeneration, especially the neovascular form of the di sease, is the loading cause of blindness in elderly people in developed cou ntries. Thermal photocoagulation is still the preferred treatment for choro idal neovascularization that does not involve the fovea, but it is suitable for only a small number of patients and it can lead to immediate loss of v isual acuity. Photodynamic therapy with use of photochemical light activati on of verteporfin as a photosensitizer (verteporfin therapy) has been shown to be effective in treating vascularized tumors, and its potential to trea t other conditions involving neovascularization has also been suggested. Pr eclinical and clinical studies have indicated that verteporfin therapy can be used to treat choroidal neovascularization secondary to age-related macu lar degeneration effectively and safely. Selective occlusion of choroidal n eovasculature by this therapy causes minimal damage to the neurosensory ret ina and, therefore, does not induce loss of visual acuity. This benefit all ows verteporfin therapy to be used in the large proportion of patients who are not eligible for treatment by laser photocoagulation. The mechanistic a spects of the mode of action of light-activated verteporfin are described i n this review. (Surv Ophthalmol 45:195-214, 2000. (C) 2000 by Elsevier Scie nce Inc. All rights reserved.).