 The main cause of severe vision loss in patients with age-related macular degeneration AMD is the development of choroidal neovascularization CNV. This debilitating form of AMD affects the macula lutea, the central part of the retina, which is responsible for high resolution visual acuity. Characteristic findings in neovascular AMD include the development of new, abnormal blood vessels in the choroid layer beneath the macula otherwise known as CNV. 