It was a small fraction of the total number of cells. This would be the functional equivalent in humans of going from completely blind to being able to make out large objects and their position in a room, says Huberman. The research may pave way for new directions that can help millions who suffer from vision loss.
But the research provides a hope that there is a way to find a solution.
Importantly, while retinal ganglion cells' axons in the crushed optic nerve had been obliterated, the front-line photoreceptor cells and those cells' connections to the retinal ganglion cells in the damaged eye remained intact. They then set about trying to fix the nerve they'd damaged, using different therapies.
But neither approach alone could re-establish the link between brain and eye.
On its own, injecting a virus that reactivates a growth pathway called mTOR also got the RGCs to regenerate partially. Huberman believes that therapies building on these results could include filters for VR games and TV programs, or simply glasses that deliver regeneration-inducing visual stimulation. Mice were placed in "IMAX theater" and using their damaged eye, the mice watched a series of high-contrast moving bars. The experiments were able to force them into regeneration and to reconnect with the appropriate parts of the brain.
"When we did that, we saw an incredible synergistic effect", Huberman said.
The retina, a thin layer of cells lining the back of the eye, converts light into electrical signals and sends them to the brain so we can see.
Moreover, a number of the vision tests found a degree of restored sight.
"It means that neurons remember the way home; they never forget", Huberman said. One thing that researchers agree with is it would be hard to treat glaucoma-created blindness in humans.
Scientific experimentation at Stanford University has managed to partially restore vision in blind mice for the first time.
"More than a third of the human brain is dedicated to the processing of visual information", he said. "They went to the right places, and they did not go to the wrong places", Dr. Huberman explained in a statement.
"This data shows that there is a bridge to get to the other side of this, to go from being on defense to being on offense, where we can help people see", said Iwach, an associate clinical professor of ophthalmology at the University of California, San Francisco. "Now, we need to think about what type of patient might be most likely to benefit from the treatment".
The scientists experimented on mice that had damage to their optic nerves, which connect the eyes and brain.
In the study, the researchers conducted treatments on adult mice which each had damage to the optic nerve in one eye. "Glaucoma is not as clean and easy as crushing the nerve, which is quick and dirty and all the nerve cells die at once".
Here's what Huberman's team did. Test mice - genetically engineered to produce higher levels of a protein called mTOR in their retinal nerve cells - had their optic nerve crushed behind one eyeball.
The mice were tested three weeks later for their ability to respond to certain visual stimuli, and their brains were examined to see if any axonal regrowth had occurred.
Huberman also is working with researchers in virtual reality, gaming, and phone software to develop programs that will work like an IMAX for mice as a way to stimulate connections through the optic nerve. This method worked ... sort of. The neural axons showed some growth back towards the brain, but not enough to reestablish connection. The mice were are blind as they were without treatment.