Scientists from EPFL in Switzerland and Scuola Superiore Sant”Anna in Italy are developing technology for the blind that bypasses the eyeball entirely and sends messages to the brain.
They do this by stimulating the optic nerve with a new type of intraneural electrode called OpticSELINE.
Successfully tested in rabbits, they report their results in Nature Biomedical Engineering.
“We believe that intraneural stimulation can be a valuable solution for several neuroprosthetic devices for sensory and motor function restoration.
The translational potentials of this approach are indeed extremely promising,” explains Silvestro Micera, EPFL’s Bertarelli Foundation Chair in Translational Neuroengineering, and Professor of Bioelectronics at Scuola Superiore Sant”Anna, who continues to innovate in hand prosthetics for amputees using intraneural electrodes.
Blindness affects an estimated 39 million people in the world.
Many factors can induce blindness, like genetics, retinal detachment, trauma, stroke in the visual cortex, glaucoma, cataract, inflammation or infection.
Some blindness is temporary and can be treated medically. How do you help someone who is permanently blind?
The idea is to produce phosphenes, the sensation of seeing light in the form of white patterns, without seeing light directly.
Retinal implants, a prosthetic device for helping the blind, suffer from exclusion criteria.
For example, half a million people worldwide are blind due to Retinitis pigmentosa, a genetic disorder, but only a few hundred patients qualify for retinal implants for clinical reasons.
A brain implant that stimulates the visual cortex directly is another strategy albeit risky.
A priori, the new intraneural solution minimizes exclusion criteria since the optic nerve and the pathway to the brain are often intact.
Previous attempts to stimulate the optic nerve in the 1990s provided inconclusive results. EPFL’s Medtronic Chair in Neuroengineering Diego Ghezzi explains, “Back then, they used cuff nerve electrodes.
The problem is that these electrodes are rigid and they move around, so the electrical stimulation of the nerve fibers becomes unstable.
The patients had a difficult time interpreting the stimulation, because they kept on seeing something different.
Moreover, they probably have limited selectivity because they recruited superficial fibers.”
Intraneural electrodes may indeed be the answer for providing rich visual information to the subjects.
They are also stable and less likely to move around once implanted in a subject, according to the scientists.
Cuff electrodes are surgically placed around the nerve, whereas intraneural electrodes pierce through the nerve.
Together, Ghezzi, Micera and their teams engineered the OpticSELINE, an electrode array of 12 electrodes.
In order to understand how effective these electrodes are at stimulating the various nerve fibers within the optic nerve, the scientists delivered electric current to the optic nerve via OpticSELINE and measured the brain’s activity in the visual cortex.
They developed an elaborate algorithm to decode the cortical signals.
They showed that each stimulating electrode induces a specific and unique pattern of cortical activation, suggesting that intraneural stimulation of the optic nerve is selective and informative.
As a preliminary study, the visual perception behind these cortical patterns remains unknown.
Ghezzi continues, “For now, we know that intraneural stimulation has the potential to provide informative visual patterns.
It will take feedback from patients in future clinical trials in order to fine-tune those patterns. From a purely technological perspective, we could do clinical trials tomorrow.”
With current electrode technology, a human OpticSELINE could consist of up to 48-60 electrodes.
This limited number of electrodes is not sufficient to restore sight entirely.
But these limited visual signals could be engineered to provide a visual aid for daily living.
In an extraordinary medical trial, six blind people have now had their vision partially restored thanks to Orion, a new device that feeds images from a camera directly into the brain – and they may just be the first of many to benefit from the cutting-edge tech.
“By bypassing the eye completely you open the potential up to many, many more people,” Optegra Eye Hospital surgeon Alex Shortt, who wasn’t involved with the research, told The Daily Mail.
“This is a complete paradigm shift for treating people with complete blindness. It is a real message of hope.”
Stimulating Science
The Orion device comprises two main parts: a brain implant and a pair of glasses.
The implant consists of 60 electrodes that receive information from a camera mounted on the glasses.
Together, they can deliver visual information directly to the wearer’s brain, removing the eyes from the equation entirely.
“If you can imagine every spot in the visual field in the visual world, there’s a corresponding part of the brain that represents that area, that spatial location,” researcher Daniel Yoshor explained in a video on the tech.
“And we know that if we stimulate someone’s brain… in a specific spot, we will produce a perception of a spot of light corresponding to that map in the visual world.”
To test their device, the researchers asked completely blind participants in an early feasibility study to look at a black computer screen while using Orion.
When a white square would randomly appear on the screen, the participants could correctly point to the square the majority of the time.
Square One
Yoshor believes that the white square may be just the start of restoring vision to blind patients.
“Theoretically, if we had hundreds of thousands of electrodes in the brain we could produce a rich visual image,” he said in a press release.
“Think of a painting that uses pointillism, where thousands of tiny spots come together to create a full image. We could potentially do the same by stimulating thousands of spots on the occipital part of the brain.”
Still, even in its current state, the device is already changing lives.
“It is awe inspiring to see so much beauty,” Benjamin James Spencer, a 35-year-old study participant who has been blind since age nine, told The Daily Mail, noting his new ability to see his wife’s face shape and his kids running up to him for a hug.
“It is not perfect vision — it is like grainy 1980s surveillance video footage,” Spencer added. “It may not be full vision yet, but it’s something.”
More information:Nature Biomedical Engineering (2019). DOI: 10.1038/s41551-019-0446-8 , https://www.nature.com/articles/s41551-019-0446-8
Journal information: Nature Biomedical Engineering
Provided by Ecole Polytechnique Federale de Lausanne
