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eye to release proteins that slow the decay of light-responding cells. And with BrainPort, a
camera worn by a blind person captures images and transmits signals to electrodes slipped onto
the tongue, causing tingling sensations that a person can learn to decipher as the location and
movement of objects.
Ms. Campbell's artificial retina works similarly, except it produces the sensation of sight, not
tingling on the tongue. Developed by Dr. Mark S. Humayun, a retinal surgeon at the University
of Southern California, it drew on cochlear implants for the deaf and is partly financed by a
cochlear implant maker.
It is so far being used in people with retinitis pigmentosa, in which photoreceptor cells, which
take in light, deteriorate.
Gerald J. Chader, chief scientific officer at the University of Southern California's Doheny
Retinal Institute, where Dr. Humayun works, said it should also work for severe cases of age-
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