Scientists plan to test an implanted chip with four times the resolution of the previous version in people blinded by retinal degeneration It now has 60 pixels instead of 16 and because it is smaller the operation to implant it is much less traumatic, taking just 90 minutes instead of eight hours. Prof Humayun predicts that it will cost around $30,000 (£15,400).
Both Chichilnisky and the USC researchers are working with Second Sight Medical Products, the company based in Sylmar, CA, that is manufacturing the devices, on the next version of the implant. The third-generation device will have 500 electrodes, boosting resolution by a factor of almost 10.
But increasing the number of electrodes won’t be the only hurdle in developing implants that can give blind people truly useful vision. Scientists also need to figure out how to electrically stimulate the retina in a way that the brain can interpret with high spatial resolution, says Joseph Rizzo, an ophthalmologist at the Massachusetts Eye and Ear Infirmary and codirector of the Boston Retinal Implant Project. A ray of light, for example, stimulates retinal cells in a more precise and refined way than does the electric current coming from an electrode. “It doesn’t matter if you have 10 or 1,000 electrodes,” he says. “If you don’t know how to use them, it doesn’t matter.”
A tiny implant on the surface of the eye receives wireless signals from an external camera, which the patient wears on a pair of glasses. The implant transmits signals to an array of electrodes surgically implanted on the retina. The array delivers electrical signals to the nerve cells in the eye, mimicking the role of light-sensitive cells lost in degenerative retinal disease.
Credit: Courtesy of Doheny Eye Institute
How the retinal implant works. Photograph: University of Southern California
Increasing electrodes is also a goal of improved cochlear implants which is discussed at wikipedia.
Biological cures for regenerating or growing the necessary visual or hearing systems is also possible path to future treatment.