Implants can also help when a sense has already been lost or is compromised. The Argus II implant from Second Sight Medical is a great example of this. The system comprises glasses with a build-in camera. The signals are sent to an electrode array implanted on the patient’s retinal surface. The array stimulates the optic nerve and allows people who are blind due to retinitis pigmentosa to see shapes and contrasting light and dark patterned images again. By now, Argus II has been replaced by the Orion system, a brain implant with electrodes that can deliver an image to the visual part of the brain. An early feasibility study of the Orion Cortical Visual Prosthesis is underway in the U.S.
For years, a similar concept comes into play to help patients with hearing loss. A cochlear implant is an electronic device that is embedded in the cochlea where it electrically stimulates the auditory nerves. Unfortunately, today's cochlear implants have a major drawback: "Implant wearers (thus) can find it difficult to distinguish between pitches, which means they have a harder time understanding spoken language, and this often also affects their enjoyment of music," Prof. Tobias Moser explains in a MEDICA-tradefair.com interview.
The electric current spreads widely along the human cochlea, thus stimulating many nerve cells at the same time. Moser and his "OptoHear" project team want to solve this problem with optical fibers, since "light can be more easily focused and spatially confined, certain regions in the cochlea can be stimulated better with light versus electrical pulses."
Nerve cells are not light-sensitive by nature and must therefore be genetically adapted, meaning the researchers' first step is to develop a successful gene therapy. It should prompt the formation of new pores in the nerve cells that open when light hits. This excites the nerve fiber and sends an impulse to the brain. The method is currently still being explored in animal research. According to Moser, the first optical cochlear implant could be available as early as the late 2020s.