Restoring eyesight has been a big challenge for scientists. Engineers from EPFL have developed a retinal implant technology that seeks to solve this challenge. The research was published in Communication Materials.
Diego Ghezzi, holder of the Medtronic Chair in Neuroengineering (LNE) at EPFL’s School of Engineering has made the issue of restoring eyesight his research focus. His team have been working on a retinal implant that works with camera-equipped smart glasses and a microcomputer. Ghezzi says, “Our system is designed to give blind people a form of artificial vision by using electrodes to stimulate their retinal cells.”
How does the retinal implant work?
The camera in the smart glass takes an image of the person’s field of vision. Then, data is sent to a microcomputer which is placed in the end piece of one of the eyeglasses. The data is converted to light signals by the microcomputer and is transmitted to the electrode in the retinal implant.
The wearer now sees a simplified, black and white version of the image, made up of dots of light. The user must learn to interpret these dots to figure out shapes and objects. Ghezzi explains, “It’s like when you look at stars in the night sky—you can learn to recognize specific constellations. Blind patients would see something similar with our system.”
However, this technology hasn’t been tested on humans yet. Before doing this, the team needs to be certain of their results. Ghezzi says, “We aren’t yet authorized to implant our device in human patients, since obtaining the medical approval takes a long time. But we came up with a process for testing it virtually—a type of workaround.” This essentially implies that the team has created a virtual reality simulation of what the patients would see with the help of the implant.
Field Vision and Resolution
Vision is measured using two parameters: field of vision and resolution. The engineers also used these two parameters to evaluate their technology. The retinal implant contains 10,500 electrodes, each one generating a dot of light. “We weren’t sure if this would be too many electrodes or not enough. We had to find just the right number so that the reproduced image doesn’t become too hard to make out. The dots have to be far enough apart that patients can distinguish two of them close to each other, but there has to be enough of them to provide sufficient image resolution,” says Ghezzi.
Another challenge was making sure that the electrode could reliably and efficiently produce a dot of light. Ghezzi explains, “We wanted to make sure that two electrodes don’t stimulate the same part of the retina. So we carried out electrophysiological tests that involved recording the activity of retinal ganglion cells. And the results confirmed that each electrode does indeed activate a different part of the retina.”
Once this was done, the next step was to figure out, using virtual reality, whether the 10,500 light dots give good enough a resolution. “Our simulations showed that the chosen number of dots, and therefore of electrodes, works well. Using any more wouldn’t deliver any real benefits to patients in terms of definition,” says Ghezzi.
The team tested the retinal implants at constant resolution while changing field of vision angles. Ghezzi says. “We started at five degrees and opened up the field all the way to 45 degrees. We found that the saturation point is 35 degrees—the object remains stable beyond that point.”
The results of these experiments were positive, and it showed the team that it is ready for clinical trials. However, it is going to be a while before the retinal implant can be used on actual patients.