When neurologists first found a way to regrow damaged optic nerves in mammals 5 years ago, they weren't sure exactly how the procedure worked. Now, a team of researchers has identified the molecule responsible and achieved significant regeneration of optic nerves in rats without the harmful side-effects seen with some previous techniques. The optic nerve connects the eye to the brain. Injuries or diseases such as glaucoma can damage it, and once severed, nerve fibers projecting from the retina via the optic nerve don't regrow. In the past, scientists have achieved modest sprouting of these neurons in rats by inducing...