Scientists say they've restored the vision of blind mice by introducing light-sensitive cells into the rodents' retinas. These "photoreceptor precursor cells" are not undifferentiated stem cells but come from a later stage of cell development when stem cells have already "committed" to being a particular cell type -- in this case the rod-and-cone photoreceptors the eye uses to sense light.The study invigorates the search for cell transplants that might someday restore the vision of millions of people who suffer from a loss of these photoreceptors. "We think this is a major breakthrough because it shows what can be achieved," said...