Researchers at Sandia National Labs have developed the Multiple-unit Artificial Retinal Chipset, which sits inside the eye. It is aimed at those suffering from macular degeneration and retinitis pigmentosa, where the light-sensitive cells on the retina stop working but the nerves survive.
The project, which is funded by a $9 million, three-year grant from the Department of Energy?s Office of Biological and Environmental Research, is a collaboration between U.S. national research labs and universities.
"The aim is to bring a blind person to the point where he or she can read, move around objects in the house and do basic household chores," Sandia National Labs project leader Kurt Wessendorf said in a statement.
"They won't be able to drive cars, at least in the near future, because instead of millions of pixels, they'll see approximately a thousand. The images will come a little slowly and appear yellow. But people who are blind will see."
The system involves multiple components mounted both inside and outside the eye. A spectacle-mounted camera takes video that is then processed and transmitted into the eye by radio. There, a chip made from micro-machined silicon and protective coatings receives the signal and extracts data with which to stimulate the retinal nerves. Like a crystal radio set, it also extracts the power it needs to run from the radio signal, removing the need for any external wires or internal power pack.
The mammalian eye has an evolutionary flaw, whereby the cones and rods lie behind the layer of neurons that feed the optic nerve. This reduces visual acuity and gives humans a blind spot, but is actually helpful when it comes to wiring up retinal implants. The chipset receiver sits on top of the retina, making direct contact with the nerves through an array of electrodes.
By designing the chipset receiver to have the same buoyancy as the fluid in the eye, and by doing as much processing outside as possible, the stress on the retina and any heat dissipation problems are kept to a minimum.
The whole system is the result of research at John Hopkins and North Carolina State universities, the University of Southern California and Oak Ridge National Laboratories. Other labs, such as Sandia, Los Alamos and Laurence Livermore, are modeling neural pathways and testing new materials.
Many problems and questions remain, such as the best waveform for stimulating the nerves, the best way to package the chip to keep it and the eye healthy, the best way to connect the chip to the retina, and how to transmit color images. The project is due to be finished in 2004, by which time the team hope the picture will be sharp enough to distinguish text and faces, and could be available as a treatment for blindness.