Implants powered by light! By using photovoltaic technology, scientists might one day reverse vision loss with a simple surgery to insert self-powered implants that don’t require an external power supply.
Light receptors in the retina transform light hitting the eye into electrical impulses; damages to photoreceptors prevent visual information from being sent to the brain. Retinal prostheses can replace damaged photoreceptors – but current devices are typically powered by inductive coils, requiring complex surgical procedures to implant the components necessary for a power supply.
So Stanford’s James Loudin and colleagues developed a self-powered system. So far, it’s only been tested with rats, but it’s got the potential to restore vision in people using the fewest implanted components.
The system consists of special goggles that fire infrared signals into the eye and onto a retinal implant. Each pixel in the implant is fitted with silicon photodiodes – photovoltaic pixels similar to those found in rooftop panels.
In Star Trek terms: like Geordi LaForge’s visor, Loudin says, these patients cannot see without the goggles. The details (also pictured above):
- A portable computer processes video images captured by a little camera mounted onto a pair of goggles.
- Then the video goggles project these images onto the retina using pulses of near-infrared light (which won’t damage or heat up eye tissues).
- Finally, pixels in the photodiode array convert this light into electrical currents, stimulating the retinal neurons.
The infrared pulses emitted by the goggles transmit transmit both visual data and power directly to the photovoltaic implants, eliminating the need for any bulky external power source.
Since the pixels are only 70 micrometers wide (one-third of the width of a human hair), each can be activated individually. This is similar to the way real photoreceptors work and could lead to better resolutions.
The work was published in Nature Photonics yesterday.
Image of eye by _StaR_DusT_ via Flickr / figure above from K. Mathieson et al., Nature Photonics