Thanks to tiny technology, victims of retitinitis pigmentosa (RP) and age-related macular degeneration (AMD) may be able to see again someday. The Food and Drug Administration has approved clinical trials of the Argus II Retinal Prosthesis System, which is the next phase of a collaboration between the University of Southern California Doheny Eye Institute, Second Sight Medical Products, and the Department of Energy.
Diseases like RP and AMD attack the retina's photoreceptor cells, which then degenerate and fail to capture and process light. The technology comprises a camera and microprocessor mounted in eyeglasses, a receiver implanted behind the ear, and an electrode-studded array that's attached to the retina. The array takes the place of the damaged photoreceptors.
The camera sends images to the microprocessor, which transmits a signal to the receiver. Using a tiny cable, the receiver sends the signal to the array, which then emits pulses that travel along the optic nerve to the brain. The brain perceives patterns of light and dark spots corresponding to the stimulated electrodes.
USC and Second Sight tested the first-generation Argus 16, with an array of 16 electrodes, on six patients. All of the patients now can detect light, count discrete items, locate and differentiate objects in their environment, and even perceive motion. The Argus II's 60-electrode array should offer better resolution.
Already, work is under way on a model that will be a fraction the size of the current devices yet include up to 200 electrodes. Such a device must be biocompatible with delicate eye tissue yet able to withstand the eye's corrosive, salty environment. It also must stay attached to the retina without compressing or pulling the tissue. And, it needs to draw enough power to function without generating the kind of heat that would damage what remains of the retina. The DoE has enlisted its member labs to solve these challenges.