Brain implant restores vision to a man blinded by an optic nerve injury

At Christmas 2018, Miguel Terol suddenly lost sight in his right eye. Six weeks later, he felt something strange in his other eye. He went to the emergency room, and while waiting there, he felt his vision dimming. Frightened, he started shouting, “I can’t see, I can’t see!” At the hospital, he was diagnosed with non-arteritic anterior ischemic optic neuropathy (NAION), a sudden loss of vision caused by a lack of blood flow to the optic nerve. “It’s a type of stroke that affects the eyes,” Terol explains. His neurologist told him about an experimental trial at the Miguel Hernández University (UMH) in Elche. In June 2022, in the midst of the pandemic, they opened his head to place a tiny 4x4 millimeter implant with 100 microneedles in his visual cortex, in the back of his neck. They were trying to stimulate the cortex to reproduce visual perceptions. Although the trial was intended to validate the technology, he regained enough vision to perceive light, detect movement, identify objects, and even read large characters on a screen. It was unexpected. And although it’s just one case, it will serve as the basis for testing it with others.

Two days after the implant, while still in the hospital, Terol asked one of the healthcare workers if he was moving his arms. “The doctors, the scientists, everyone got nervous,” he recalls. His wife, also in the room at that moment, became concerned, asking what they had done to him. Eduardo Fernández, director of the UMH Bioengineering Institute and head of the trial in which Terol had enrolled, remained calm. Based on previous work, such as that of Bernadeta Gómez, who partially recovered her sight via the same system in 2021, Fernández knew that, after this type of implant, patients could regain some vision through a placebo-like effect.

“Berna had visual hallucinations, but with Terol, the recovery was real. We ran a series of tests and saw that he had recovered some of his visual perception,” says Fernández, senior author of this research, the results of which have been published in the scientific journal Brain Communications. “He wasn’t seeing lights; he was seeing what was right in front of him,” he adds. It was completely unexpected. Firstly, because it was very early; they hadn’t even started training the system. Secondly, because in other similar recoveries, the patients had recent optic nerve injuries, not from almost four years ago. But more importantly, “the study design wasn’t intended to improve vision with Terol; it was about seeing if we could induce perceptions,” Fernández explains.

The design aimed to evaluate the safety and feasibility of a cortical visual prosthesis based on neurostimulation, for which they later intend to assess its effectiveness. Electrical brain stimulation is opening up countless possibilities, especially for people whose abilities are limited for any reason, such as communication failures between the head and the rest of the body. Thus, various technologies have enabled communication for people who could not speak, including a woman who could only blink, or even to write using the mind. To put it simply, similar approaches have given hope to people with spinal cord injuries or Parkinson’s disease. The idea is always the same: to bypass the damaged area to reconnect the hand, foot, mouth, or eyes with the part of the brain that processes each type of information.

“The procedure involved the surgical implantation of an intracortical array of 100 microelectrodes in the primary visual cortex, the region of the brain responsible for processing visual information,” explains Arantxa Alfaro, a neurologist at the Vega Baja Hospital in Orihuela, who first treated Terol when he went blind. The implant is connected to glasses that act as an artificial eye, encoding what is in front of it and converting it into the type of signals the brain understands: electrical signals.

For six months, Monday through Friday, for three to four hours a day, the participants in the trial trained the system, fine-tuning it and setting thresholds. “They would put things in front of me, images and numbers on the screen, they would flash the camera at me…” says Terol, who was the director of Radio Elche when he went blind. “One exercise was called the ‘sock omelet.’ They would put 10 pairs of white socks, 10 pairs of black socks, and another 10 pairs of gray socks, in different shades, and I had to classify them,” recalls the candidate for mayor of Redován in the last elections.

After that time, Terol was afraid again. He didn’t see as he could before, but he could perceive light, shapes, movement; he could distinguish between a knife and a fork, an apple from an orange; he could modulate the distance of his hands to pick up something fragile like a plate or grasp a block of wood... But it was time to take him back to the operating room to remove the implant. “The scientists expected that, without it, I would lose what I had gained,” he says over the phone. But three years have passed since it was removed and seven since that terrible Christmas, “and I’ve lost some vision, but I still have it; I’m proud to participate in the trial,” concludes Terol, who adds that he would let them open his head again. And it’s likely that it won’t be long before they do.

“The truth is, we don’t know what happened,” admits Fernández, who has spent years studying and researching how vision works in the brain. Terol wasn’t the only participant in the study. There were three others. “The others had been blind for many years, while he had only been blind for three; that might have been a factor,” says the UMH scientist. “It might have something to do with the time course of blindness, but we only have one case.” More could be learned by performing a biopsy, which is impossible while the patient is alive. “We have studies in animals that demonstrate that electrical stimulation induces brain plasticity. Neurotransmitters are released, and there are changes in the system that enhance plasticity and probably self-repair,” Fernández also points out. He intends to retrace his steps and conduct animal trials to find molecular clues.

The human trial, for which they are already enrolling more people, is now entering its next phase. But Fernández is both hopeful and cautious: “When I was studying medicine, if a patient like this hadn’t recovered within two months, it was already irreversible; there was nothing you could do, and they would have to go to the ONCE (Spanish National Organization of the Blind).” He adds: “Now what we see is that after three years, it’s still not completely reversible, but there are options, and we should try to understand what we can do, how far we can go.” Because he doesn’t want it to be just another story like those of Miguel Terol or Bernadeta Gómez. “Perhaps it can serve as a foundation, opening new avenues, for developing new therapeutic approaches in the case of sensory pathologies like vision impairment, but also for others like stroke,” the scientist concludes.

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