Retinal prostheses have the potential to bring sight to people that would otherwise stay blind for the rest of their lives due to retinal degenerative disease. While the basics of the technology are getting ironed out, the issues of delivering power to an implant and interfacing it with an external camera remain. Wires penetrating the skin can get dirty and lead to dangerous infections, and relying on glasses-based cameras for input just doesn’t cut it for our cyborgian future.
Researchers at Stanford have been working on technology that may change all that, thanks to tiny photovoltaic modules that autonomously convert visible light to electric potentials. The system relies on electronic glasses that shine near-infrared light onto the implant, removing any wires out of the picture. The original photovoltaic pixels were somewhat large, but now they are able to make them as small as 70 μm. They successfully tested the implants in laboratory rats and identified the optimal range of frequencies and pulse durations to illicit the strongest visually evoked potentials (VEP) in the brain. By stringing together dozens of these pixels within a contact lens, the researchers hope to achieve a true retinal prosthetic that would bring sight to untold numbers of people.
From the study abstract in Nature Communications:
Each pixel in the subretinal implant directly converts pulsed light into local electric current to stimulate the nearby inner retinal neurons. Here we report that implants having pixel sizes of 280, 140 and 70 μm implanted in the subretinal space in rats with normal and degenerate retina elicit robust cortical responses upon stimulation with pulsed near-IR light. Implant-induced eVEP has shorter latency than visible light-induced VEP, its amplitude increases with peak irradiance and pulse duration, and decreases with frequency in the range of 2–20 Hz, similar to the visible light response.
Study in Nature Communications: Cortical responses elicited by photovoltaic subretinal prostheses exhibit similarities to visually evoked potentials
(hat tip: Medical Daily)