By Adrian Galbreth
Scientists at the Stanford University School of Medicine have created a system that could someday restore sight to people who have lost vision because of certain types of degenerative eye diseases.
The technique is a new type of retinal prosthesis that involves using a specially designed pair of goggles equipped with a miniature camera and a pocket PC that processes the visual data stream.
The resulting images are displayed on a liquid crystal microdisplay embedded in the goggles, similar to what is used in video goggles for gaming.
Unlike regular video goggles, images are beamed from the LCD using laser pulses of near-infrared light to a photovoltaic silicon chip, which is one-third as thin as a strand of hair and implanted beneath the retina.
Electric currents from the photodiodes on the chip trigger signals in the retina, which then flow to the brain, enabling a patient to regain vision.
A new study published online in Nature Photonics discusses how scientists tested the photovoltaic stimulation using the prosthetic device's diode arrays in rat retinas in vitro and how they elicited electric responses, which are widely accepted indicators of visual activity, from retinal cells.
The experts are now testing the system in live rats, taking both physiological and behavioural measurements, and are hoping to find a sponsor to support tests in humans, explained Dr Daniel Palanker, associate professor of ophthalmology and one of the paper's senior authors.
"It works like the solar panels on your roof, converting light into electric current. But instead of the current flowing to your refrigerator, it flows into your retina," he added.
Current implants are very bulky, and the surgery to place the intraocular wiring for receiving, processing and power is difficult, but the device developed by his team has virtually all of the hardware incorporated externally into the goggles, the expert explained.
"The surgeon needs only to create a small pocket beneath the retina and then slip the photovoltaic cells inside it. What's more, one can tile these photovoltaic cells in larger numbers inside the eye to provide a wider field of view than the other systems can offer," Dr Palanker said.
Further studies will now take place, with a view to rolling out the devices across the globe and stepping up the fight against vision loss.
by Alexa Kaczka