A new study published in the scientific journal eLife promises to help scientists refine the technology of retinal prostheses. This study was conducted primarily by scientists at the Institut de Neurosciences de la Timone and Assistance Publique Hôpitaux de Marseille. Many other scientists from prestigious French institutes collaborated in this study, including some from Aix-Marseille Université, the Institut National de la Santé, and the Centre National de la Recherche Scientifique.
Retinal prostheses are implanted in a blind patient's eyes to help restore some semblance of sight. Current retinal prostheses feature a camera on the patient's spectacles, an electronic microcircuit, and a bunch of microscopic electrodes placed right in the patient's retina. This whole design is understood to help the eye convert electrical currents into visual signals to be interpreted by the brain. The electronic microcircuit is tasked with converting the visual stimuli given off by the camera into an electrical signal. Only patients with healthy optical nerves can benefit from this device, since the optical nerve is still needed to send the signal to the brain. Serious research has been going on for ten years with this technology.
While retinal prostheses have been able to restore a hazy quality of vision to patients, they are still very far from helping blind people see with full clarity. People who use retinal prostheses say that they can make out light spots and large objects, but they struggle to recognize more nuanced material like faces or words in a book.
To understand better about how retinal prostheses work, and how to increase their efficacy in the future, scientists took a bunch of rodents and examined how their visual cortex reacted to both normal visual stimulation and stimulation from retinal prostheses. The main difference scientists observed in this study was that the rodents' visual cortexes were activated to a greater extent by stimulation through the retinal prostheses. Also, the images rodents perceived through the retinal prostheses were wider than those processed with normal light.
To account for these findings, scientists say that current retinal prostheses give off too much electrical diffusion. Also, researchers found that excess retinal fibers close to targeted cells were being activated. The added activation of unwanted fibers could be another culprit in making the images people experience with retinal prostheses very ill defined.
Scientists hope that by reducing the currents sent off by the electronic microcircuit they will be able to increase the clarity of vision in patients eligible for retinal prostheses. With a few more tests, doctors believe they can give blind people a higher quality of sight with these amazing implants.