Dalton, a squirrel monkey treated with gene therapy, enjoys his new colour sense.Neitz Laboratory Researchers have used gene therapy to restore colour vision in two adult monkeys that have been unable to distinguish between red and green hues since birth — raising the hope of curing colour blindness and other visual disorders in humans."This is a truly amazing study," says András Komáromy, a vision researcher and veterinary ophthalmologist at the University of Pennsylvania in Philadelphia, who was not involved in the research. "If we can target gene expression specifically to cones [in humans] then this has a tremendous implication."About 1...