While similar devices require coils, cables or antennas inside the eye to transmit power and information to the retinal implant, the Stanford device uses near-infrared light to deliver images making the device thin and easily implantable. As described in our recent release:
This device — a new type of retinal prosthesis — involves a specially designed pair of goggles, which are equipped with a miniature camera and a pocket PC that is designed to process the visual data stream. The resulting images would be displayed on a liquid crystal microdisplay embedded in the goggles, similar to what’s used in video goggles for gaming. Unlike the regular video goggles, though, the images would be beamed from the LCD using laser pulses of near-infrared light to a photovoltaic silicon chip — one-third as thin as a strand of hair — implanted beneath the retina.
Electric currents from the photodiodes on the chip would then trigger signals in the retina, which then flow to the brain, enabling a patient to regain vision.
A study, published online May 13 in Nature Photonics, shows how scientists used rat retinas to assess the photodiode arrays in vitro, and how the diodes produced electric responses that are widely accepted indicators of visual activity. The scientists are now testing the system in live rats, taking both physiological and behavioral measurements, and are hoping to find a sponsor to support tests in humans.