- AMD will be defined as the presence of large ( 63 um), soft, distinct drusen with pigmentary irregularities, or indistinct (125 um) or reticular drusen, or atrophic or neovascular AMD. Atrophic AMD will be defined as any sharply demarcated round or oval areas of apparent absence of the retinal pigment epithelium larger than 175 um, irrespective of the distance from the fovea, but within the grid, with visible choroidal vessels and no neovascular AMD.