Comparison of scanning electron micrographs of ON capillary supply in Human (A), Rat (B) and Mouse (C). In humans, ON capillaries are largely derived from feeder branches (arrows) derived from the choroidal vasculature (Chor) surrounding the optic nerve (ON). Rats have a similar ON capillary structure largely derived from the choroid (Chor). In mice, the ON capillary structure is much sparser, with few capillaries draining into the central retinal vein (V). Data from (Human: Olver and McCartney, (1989); Rat: Morrison et al., (1999); Mouse: May and Lutjen-Drecoll, (2002). Scale bar: 1 micron.