In conducting their experiments, researchers manipulated optic-nerve cables, which help convey visual information from the eye to the brain, to regenerate after being completely severed. Incredibly, they discovered that these cables could actually re-establish connections with parts of the brain. Before the eye-brain connection was re-established, the mice suffered from a condition similar to glaucoma, which is currently the second-leading cause of blindness. And given that there’s no cure today for glaucoma, these findings could be a major breakthrough in the vision world.
The key to this regeneration appears to lie in a cascade of growth-enhancing chemical reactions, known as the mTOR pathway. In their experiments, the Stanford team boosted the pathway’s activity. Mice with a damaged optic nerve were either treated with gene therapy targeting the mTOR pathway, images of a moving black-and-white grid, or both.
After three weeks, scientists found that when both approaches were used and the undamaged eye was covered to encourage the use of the problem eye, the optic-nerve axons regenerated, all the way to the brain.
“Somehow these retinal ganglion cells’ axons retained their own GPS systems,” said Andrew Huberman, the study’s senior author. “They went to the right places, and they did not go to the wrong places.”
He added, “Several dozen mice had vision restored to varying degrees.” But varying degrees is a strong qualifier — in some vision tests (like avoiding a cliff), certain mice still failed. This, Huberman said, is because “only a very small fraction of neurons regenerated — probably less than 5 percent.”
So while we may be closer than before to restoring vision, the future is not yet crystal clear.
