- A group of researchers recently attempted to use a microelectrode array to help a blind person perceive letters and shapes.
- The implant, which is about the size of a penny, bypasses the optic nerve and instead provides stimulation to the brain’s visual cortex.
- By the end of the study, the participant could identify several letters.
According to the Centers for Disease Control and Prevention (CDC), approximately 1 million people in the United States over the age of 40 years are blind.
Although there is currently no cure for blindness, a new implantable device may one day become a useful way to increase the independence of blind people. The implant uses an electrode to provide artificial vision.
Although the device is in the early stages of clinical development, the first experiment in a human participant was successful. The results now appear in The Journal of Clinical Investigation.
The innovative study was conducted by researchers in Spain who collaborated with scientists at the Netherlands Institute for Neuroscience in Amsterdam and the University of Utah in Salt Lake City.
Phosphenes
Blind people experience a phenomenon called spontaneous phosphenes. Phosphenes are what blind people “see” when random flashes of light appear without any light entering the eye.
Sighted people can also experience phosphenes. For example, pressure phosphenes occur when a person rubs their eye. Certain drugs, ionizing radiation, and electrical and magnetic stimulation can also trigger phosphenes.
Although spontaneous phosphenes do not provide any functional vision, their manipulation played a vital role in the recent study.
Brain implant
In the study, the researchers implanted a Utah electrode array (UAE) directly into the visual cortex of the participant’s brain. The visual cortex is responsible for processing visual information. The UAE consisted of 96 microelectrodes projecting out from a silicon base.
“A long-held dream of scientists is to transfer information directly to the visual cortex of blind individuals, thereby restoring a rudimentary form of sight,” write the authors. “However, no clinically available cortical visual prosthesis yet exists.”
The study took place over 6 months and included a single participant: a 57-year-old woman who became blind 16 years before the start of the study.
Once the scientists had implanted the device, the participant had a few weeks to recover. Before the researchers could start testing the device, they needed to work with the participant to ensure that she could tell the difference between spontaneous phosphenes and the phosphenes the team wanted to induce as part of providing functional vision.
Once they determined that the participant was able to identify the induced phosphenes with 95% accuracy, the researchers began training and started presenting her with actual visual challenges.
Training sessions generally took place on 5 days per week, once or twice per day, and for up to 4 hours per session. This continued for 6 months. The scientists synced up a pair of special glasses to the implant so that they could track the participant’s eye movements.
Over the course of the study, the participant became able to identify phosphenes in a certain space.
The researchers found that it was easier for the participant to perceive the spots of light when they simultaneously stimulated more than two electrodes. Spacing out the stimulating electrodes also improved results in terms of letter and shape recognition.
“This suggests that the phosphene’s size and appearance is not only a function of the number of electrodes being stimulated, but also of their spatial distribution,” write the authors.
By the end of the study, when the team simultaneously stimulated up to 16 electrodes in different patterns, the participant was able to identify multiple letters and even tell the difference between some uppercase and lowercase letters.
Lead study author Dr. Eduardo Fernández spoke with Medical News Today about the research.
“I would like to emphasize that although our preliminary results are very encouraging, we should be aware that this is still research and not yet a clinical treatment,” said Dr. Fernández.
“In this context, the scientific and technological problems associated with safe and effective communication with the brain are very complex, and many problems have to be solved before a cortical visual neuroprosthesis can be considered a viable clinical therapy or option.”
Dr. Fernández is a professor of cellular biology and the chairman of the Department of Histology and Anatomy at University Miguel Hernández (UMH) in Alicante, Spain. He is also the director of the Neuroengineering and Neuroprosthesis Unit at the Bioengineering Institute at UMH.
Implications of study
The purpose of the implant is not to restore full vision but to provide a degree of functional vision.
“One goal of this research is to give a blind person more mobility,” says senior study author Dr. Richard Normann, a bioengineer from the University of Utah.
“It could allow them to identify a person, doorways, or cars easily. It could increase independence and safety. That’s what we’re working toward,” said Dr. Normann.
Dr. Fernández elaborated on trying to provide functional vision with the implant.
“We are not trying to provide [full vision], that right now is not feasible, but just to provide […] useful vision, for tasks such as orientation, mobility, reading big characters, etc.,” said Dr. Fernández.
“We have to go step by step and […] not create false expectations or underrate the challenges that still remain to be resolved,” Dr. Fernández continued. “In this framework, we propose that increased collaborations among clinicians, basic researchers, engineers, and associations of blind [people] [are] key to advance in this field.”
John Nosta, the founder of NostaLab and a member of the Digital Health Roster of Experts at the World Health Organization (WHO), spoke with MNT about the brain implant. He said:
“[This is] certainly an important step forward that builds upon the existing brain interface technologies, like the cochlear implant and deep brain stimulation for movement disorders.”
Conflict of interest
It is important to note that two of the study authors, Pieter R. Roelfsema and Xing Chen, are co-founders of and shareholders in a neurotechnology start-up called Phosphoenix.
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