A micro-implant could in the future enable blind people to regain basic visual skills. First attempts on a Spanish woman who had been blind for 16 years yielded promising results. The 57-year-old woman at the time of the experiments wore special glasses with a camera that sent her data to the implant in the subject’s visual cortex. The electrodes in her brain then stimulated the neurons in such a way that she had the impression of perceiving light. This enabled the subject to see shapes and even play a simple video game.
In order for us to be able to see something, our eyes and our brain have to work together: The receptors in our eyes perceive light stimuli, convert them into electrical nerve signals and send them via the optic nerve to the neurons in the visual cortex of our brain. There the signals are processed and put together to form an image. If the eyes, the visual cortex or the nerve connections between them are damaged, we can no longer see – at least so far.
Signals directly in the brain
A study by researchers led by Eduardo Fernández from the University of Miguel Hernández in Spain now gives hope that the blind might be able to regain at least some of their vision with technical help in the future. To do this, the scientists developed a tiny implant that is able to stimulate the neurons in the visual cortex. The signals do not come from the eyes, but from a small camera attached to special glasses.
The tester of this artificial vision system was Bernardeta Gómes, who was 57 years old from Spain at the time of the tests. 16 years earlier, she was completely blind from toxic substances that destroyed her optic nerves. Although signals from her eyes no longer reached her brain, she occasionally perceived what are known as phosphenes – light phenomena that are not due to actual light, but to other stimuli. We achieve a similar effect if we close our eyes and carefully press the eyeballs. Such phosphenes are not uncommon in the blind. Fernández and his colleagues took advantage of this phenomenon for their visual prosthesis.
Shapes from points of light
To enable Gómez to see fundamentally again, the researchers implanted a 3.6 by 3.6 millimeter chip with electrodes into the visual cortex of her brain. This chip was able to record the electrical activity of the neurons as well as to stimulate it – and through this stimulation it was able to trigger phosphenes in a targeted manner. Depending on how and where exactly the electrodes were sending signals, Gómez perceived different points of light. After about two months of daily training, she was able to distinguish these specifically generated phosphenes from spontaneously occurring ones – and to recognize how they combined to form forms. The stimulation traced the images in her brain, albeit in a rudimentary form, that the camera recorded on the special glasses.
In this way, Gómez could recognize letters, shapes and color boundaries and even play a simple video game. According to the scientists, the first results of this experiment indicate that the implant is safe even over a longer period of time. “We could not find any signs of neuronal irritation or the triggering of epileptic seizures, and the subject did not report any negative side effects of the electrical stimulation,” said the researchers. The implantation also went smoothly and the electrodes functioned unchanged over the entire six-month study period. Similar implants, which allow amputees to control artificial limbs, have been shown to be safe for years.
New opportunities for the blind
“These results are very exciting because they demonstrate both safety and effectiveness,” said Fernández. “We have made a significant step forward and shown the potential of this type of device to restore functional vision for people who have lost their vision.” In further studies, the team would like to work on improving the spatial resolution of the images generated and test the system with more subjects and over a longer period of time. “One goal of this research is to give blind people more mobility,” says co-author Richard Normann of the University of Utah in Salt Lake City. “It could make it easier for them to see people, doorways or cars. That could increase independence and security. This is what we are working towards. “
Source: Eduardo Fernández (Miguel Hernández University, Elche, Spain) et al., Journal of Clinical Investigation, doi: 10.1172 / JCI151331