Our ability to see depends on two factors: light-sensitive rods and cones in the retina, and the nerves that transmit signals from these cells to the brain (along with the brain itself, of course). When the rods and cones die, which can occur as the eye ages
or in the retina-damaging eye disease retinitis pigmentosa
, the nerves can sometimes still function---if they have a new, working sensor for light. To replace the rods and cones, previous treatments have used electronic implants, which require surgery, or gene therapy, which relies on injections deep into the eye. But in a new technique
, all it takes to restore vision---at least partially---is a much less invasive injection of the chemical AAQ. AAQ, which stands for acrylamide-azobenzene-quaternary ammonium, is a photoswitch: it changes shape when exposed to light. And when AAQ molecules bind to living cells, like the neurons that serve the eye, ...
