Image: New Scientist Less than a month ago, at the 2009 International Electron Devices Meeting (IEDM), researchers from Stanford University presented their solution for a retinal implant that has the potential to restore vision in those who lose sight due to age-related macular degeneration (AMD), retinitis pigmentosa (RP), and certain other retinal disorders. The implant is composed of solar cells embedded in a bed of flexible silicon electrodes that transfer visual images to the brain.
The human lens is curved in order to best project light rays onto the
retina, which is also curved. In Image: JonathanRossiter.comsome eye conditions, like AMD, photoreceptors in the retina are damaged,
which can result in partial or complete blindness.
Currently, photoreceptor retinal implants use tiny solar cells that are surgically arranged to deliver signals to the retina, but solar cells are flat and they require many surgeries to place and partially cover the curved retina.
"If you have a lens, the focal plane is always curved and the best
picture forms on a spherical surface," Rostam Dinyari, lead researcher on the Stanford project, said. "This is why the
retina is curved."
The Stanford University solution is to insert the solar, or photovoltaic, cells into one flexible silicon MEMS device that can be implanted on the retina in one surgery. Testing on retinas extracted from pigs show that the device can be fitted without damaging the array of solar cells.
Flexible array of solar cells. Image: IEDM
But the implant itself will not do the work of recreating vision. The implant is just part of a system created by Dinyari and his peers, which involves a video camera mounted to the side of a pair of user eyeglasses, a pocket computer that processes the video, and a projector worn on the front of the glass frame that projects images onto the photovoltaic implant.
Self-powered retinal prosthetic. Image: IEDM
The retinal implant, with solar cells that can rotate independently, produces enough electrical current to stimulate the brains neural cells that, in turn, translate the signals into vision. All elements in the system have to operate fast enough so as not to compete with any current images coming into the brain through residual retinal abilities.
AMD is the most prevalent cause of blindness in the US and what is considered the "developed world." RP affects about 1.5 million persons worldwide. The flexible solar retinal implant is a hopeful step in helping many of them regain their vision.
ref: IEDM, NewScientist, Memsnet.org, JonathanRossiter.com, AMD Alliance, ProVisu