Once the optic nerve that’s responsible for sight is damaged, it’s impossible to see again. At least that’s been the dogma. But a group of U.S. scientists has upended that thinking and helped mice with destroyed optic nerves to see again. It does not have immediate implications for humans yet, but it points researchers in promising new directions. Andrew Huberman, an associate professor of neurobiology at Stanford University, and his team describe their advance in…