A team at Stanford University is closer to creating a functional implant that can restore sight to the blind. The rig recalls Geordi LaForge’s visor from Star Trek: The Next Generation, with a pair of glasses fitted with a video camera beaming near-infrared light onto a chip implanted in retina. This implant stimulates nerves in the back of the eye, with a cable leading from the chip to a power source placed behind the ear, like a hearing aid.
The journal Nature has some details:
Recent clinical trials with multielectrode-array implants — interfaces that connect neurons to electronic circuitry — have restored some clarity of vision. But the surgery is complex and the implantation produces a range of unwanted side effects, including inflammation, loss of neurons, and an accumulation of astrocytes and microglia that form a sheath around the array. This increases the space between the electrode probes and also insulates the electrodes, reducing functionality.
Data transfer is also difficult to scale to large numbers of densely packed microelectrodes and, a major disadvantage in restoring a normal experience of vision, such systems are dependent on an external camera for retinal stimulation, so patients cannot use natural eye movements.
Loudin’s system reduces these problems because the photovoltaic implants are much thinner, and they are wireless. And the pulses deliver both visual information to the photovoltaic array and power it, reducing the number of components that need to be implanted. “Surgeons should be much happier with us. We’ve just got the one implant,” says Loudin. “Other approaches require pretty big pieces of hardware to be stuck in the body: 1–2 centimetres in size.”
The photovoltaic system also enables patients to scan the visual scene with their own eyes, within the visual field of the goggles.
Eberhart Zrenner at Tübingen University in Germany, a leader in the field and the co-inventor of the subretinal electronic chip, takes his hat off to the solution. “It’s an elegant approach,” he says. “It also allows for a high density of pixels, which means better resolution with many hundreds of pixels. The array is flexible, which allows larger arrays to be implanted.”
He adds that while the current demonstration is a convincing proof-of-concept, more work will be required on issues of biocompatibility, stability of the material and the development of safe surgical procedures.
Nevertheless, 66 patients in Europe and the United States have already received existing retinal-implant systems. Zrenner reckons that Loudin’s implants will be available on the market within one or two years. “There will be regulatory issues of course, but it’s coming soon.”