Stanford M.D/Ph.D. student David Purger, changes the media of retinal ganglion cells from a rat in the Monje Lab at Stanford University's Lorry I. Lokey Stem Cell Research Building, in Palo Alto, Calif. on Friday, August 31, 2012. (LiPo Ching/Staff)

Stanford M.D/Ph.D. student David Purger, changes the media of retinal ganglion cells from a rat in the Monje Lab at Stanford University's Lorry I. Lokey Stem Cell Research Building, in Palo Alto, Calif. on Friday, August 31, 2012. (LiPo Ching/Staff) (Photo by MediaNews Group/Bay Area News via Getty Images)