Isolation of RGCs by FACS. a, Dissociated retinal cells viewed under inverted phase-contrast optics before sorting. b, Field includes one fluorescent RGC (arrow) among many unlabeled cells. c, d, Analysis of retinal cells by FACS. c, x- and y-axes represent two different parameters of cell size. c′, Population of large cells analyzed further in d. d, The x-axis represents cell size; the y-axis represents intensity of fluorescence (logarithmic scale). d′, Large cells with high fluorescence selected for sorting. e, f, Cells enclosed with in d ′, viewed by phase-contrast (e) and fluorescence (f) microscopy, consist mostly of RGCs; impurities, mostly small cells, are shown with arrowheads. Scale bar, 50 μm.