Implant Thread Represents A Potential Blindness Treatment Breakthrough

A joint research effort by Chalmers University of Technology in Sweden and the Netherlands Institute for Neuroscience (NIN) at the University of Freiburg has produced a neural implant that could potentially reverse blindness.

The implant is a flexible polymer electrode and in a recent study was placed in the proverbial three blind mice, (the actual number was seven, three blind males and four females). After a year, the implant has shown that it can deliver electronic vision to the visual cortex. The results have been published in the Journal of Advanced Healthcare Materials. If they can be replicated in humans in the future, this neural implant which is no bigger than a single neuron when combined with others could restore sight to blind people.

Maria Asplund is a Professor of Bioelectronics at Chalmers. She notes that a single implant begins to eliminate the darkness. Multiples could bring back close to normal sight. The more implants, the better the image. But putting more into the brain could be overwhelming. Not so states Professor Asplund.

Each implanted device is called a thread for a good reason. They are very tiny and contain multiple aligned electrodes. An electrode the size of a neuron sounds impossible, yet advancements in nanofabrication have made it a reality.

States Professor Asplund, “Miniaturization of vision implant components is essential. Especially the electrodes, as they need to be small enough to be able to resolve stimulation to large numbers of spots in the brain visual areas.” 

Implanting several threads would put thousands of electrodes in contact with the brain’s visual areas. To restore full vision, you would probably need to implant hundreds in the visual cortex of the brain. Each is less than 15 micrometres or 15 millionths of a metre.

The study has demonstrated these implants are proving to be remarkably stable over a year and have stood up to billions of electrical pulses sent to them to train the visual cortex of the mice to see the images produced. Each of the pulses has been between 2 and 20 microamperes, far below the maximum threshold the electrodes can withstand. The natural immune response to their presence has been minimal producing little damage to the surrounding brain tissue.

The Chalmers and NIN invention improves on work previously demonstrated in 2018 by an implant invented by researchers at the John A. Moran Eye Center at the University of Utah in conjunction with Miguel Hernandez University in Spain. A penny-sized visual prosthesis made from silicon was implanted in the brain of a 58-year-old woman named Berna Gomez. She had lost her sight 16 years earlier after developing toxic optic neuropathy, a condition that destroyed her optic nerves. The Utah device allowed her to see two-dimensional shapes and letters but unfortunately degraded over time because it stimulated an immune response. Its size also made it too large to be practical for full-sight restoration.

The threadlike design of the Chalmers invention allows a large number of electrodes to be implanted within the visual cortex without overwhelming the brain. It has produced little reaction from the body’s autoimmune response. It represents a design proof-of-principle.

For more than 1 million Americans and close to 50,000 Canadians, let alone the many tens of millions on the rest of the planet, this technology could give them sight or restore it if once lost.

Testing in human hosts is still in the offing. Should human clinical trials succeed, this invention could become a promising prosthetic therapy for restoring vision through electronic stimulation of the visual cortex.