Verteporfin (trade name Visudyne), a benzoporphyrin derivative, is a medication used for the treatment of patients with predominantly classic subfoveal choroidal neovascularization due to age-related macular degeneration, pathologic myopia or presumed ocular histoplasmosis syndrome. Verteporfin can also be used to destroy tumors. Verteporfin is a 1:1 mixture of two regioisomers (I and II), VISUDYNE therapy is a two-stage process requiring administration of both verteporfin for injection and nonthermal red light. Verteporfin accumulates in these abnormal blood vessels and, when stimulated by nonthermal red light with a wavelength of 689 nm in the presence of oxygen, produces highly reactive short-lived singlet oxygen and other reactive oxygen radicals, resulting in local damage to the endothelium and blockage of the vessels. Verteporfin is also used off-label for the treatment of central serous retinopathy. Verteporfin is given intravenously, 15 minutes before laser treatment. Light activation of verteporfin results in local damage to neovascular endothelium, resulting in vessel occlusion. Damaged endothelium is known to release procoagulant and vasoactive factors through the lipo-oxygenase (leukotriene) and cyclo-oxygenase (eicosanoids such as thromboxane) pathways, resulting in platelet aggregation, fibrin clot formation and vasoconstriction. Verteporfin appears to somewhat preferentially accumulate in neovasculature, including choroidal neovasculature. However, animal models indicate that the drug is also present in the retina. Therefore, there may be collateral damage to retinal structures following photoactivation including the retinal pigmented epithelium and outer nuclear layer of the retina. The temporary occlusion of choroidal neovascularization (CNV) following VISUDYNE therapy has been confirmed in humans by fluorescein angiography.