<p>Verteporfm, when activated by low-intensity nonheat-generating laser light at a wavelength corresponding to its absorption peak, generates highly reactive, shortlived singlet 02 and reactive 02 radicals that cause local damage to neovascular endothelium, resulting in vessel occlusion. It appears to accumulate preferentially in the neovasculature e.g. choroidal neovasculature.</p>