Was Blind But Now I See

Dr. Robert Hillman places a small electrical device to his neck, holds his breath and starts silently mouthing words: "One, two, three, four, five." His words, amplified by the gizmo that purrs near his throat, are pitchless and robotic, like the voices computers had in 1960s sci-fi movies. This is how 4,000 people each year are left to communicate after the surgical removal of a cancerous larynx. The technology they use to substitute for their missing vocal cords hasn't changed much since World War II. But in a small laboratory at the Massachusetts Eye and Ear Infirmary, Hillman is trying to change that. One of his colleagues, outfitted with a small sensor on his neck, is wearing what could soon become the next-generation system for voice replacement. The goal, says Hillman: "To make it sound more like a human voice."

For centuries doctors have created prosthetic limbs for people who've lost body parts to disease, accidents or in battle. Now an elite group of researchers at Mass Eye and Ear and other institutions is working on "neural prostheses" to replace far more complicated body systems. Neural prosthetics are "devices that are designed to get information into or out of the nervous system," says Dr. William J. Heetderks, program director for Neural Prostheses at the National Institutes of Health. The devices use that information to restore functions like hearing, vision, balance or motion. When someone loses sight or hearing, it's usually because a small piece of the anatomy has malfunctioned; often the rest of the system is intact. Neural prostheses attempt to use electronics to "bypass that little section of brokenness," says Heetderks, and make the system function again.

The scientists who work in this field are cautious souls. They worry that the least bit of optimism can lead to ridiculous headlines (doctors cure blindness!) and send patients streaming to hospitals with unrealistic expectations ("I'll have the replacement eyes, please"). But much of the optimism that now exists stems from advances in the most successful area of neural prostheses: hearing replacement. Over the past 30 years more than 75,000 people worldwide have had cochlear implants to combat severe hearing loss. Today Mass Eye and Ear's Neural Prostheses Research Center still works on improving cochlear implants; the newest innovations involve implanting devices in both of a patient's ears to enhance hearing in noisy environments and allow users to better locate the source of sounds.

But down the hall from the hearing labs, Hillman and his colleagues are on the cutting edge of a related problem: improving the speech of people who've lost their voice boxes. Usually, when surgeons remove the larynx, they cut out the nerve that leads from the brain to the vocal cords. In experiments with guinea pigs, however, researcher James Heaton tried reattaching the nerve to different muscles in the neck. Then the team placed sensors on the skin, above these muscles, to try to transfer electrical impulses from the nerve to a processor (a Walkman-type device a user wears on his waist). "We're basically using the muscles as an amplifier," Heaton says. The user still speaks via an electrovibrating device pressed to the neck--the new version is held there by a brace, freeing up a user's hands--but the processor gives the device better data, allowing users to better control the pitch and volume when they speak.

Upstairs in a different lab, they're working on techniques to improve a different sense: balance. Humans achieve balance thanks largely to three semicircular organs in the inner ear, each the size of a large hoop earring. When these organs malfunction--often with age--bad things happen, including falls among the elderly. "Balance is very important; it just doesn't come up into our consciousness," says researcher Conrad Wall. With help from Draper Laboratory, a company with expertise in guided-missile technology, Wall and colleague Daniel Merfeld have devised small prostheses that connect to tiny vibrating patches attached to a user's chest and back. When a person moves, the patches begin to vibrate in distinct patterns. For example, a certain pattern of vibrations might indicate: "You're listing to starboard, mate," Wall says.

The biggest buzz in neural-prostheses research surrounds retinal implants. Researchers have already demonstrated that sending current to tiny electrodes placed on the retina of a blind person can cause some of them to see light and shapes. So teams in Europe, the United States and Asia are trying different ways to implant these devices onto a retina or directly into the brain. Using a camera mounted on a patient's glasses, they'd transmit images in the form of electric currents onto the retina the way a TV camera sends pictures to your family room. It's not clear such a system is feasible, or, if it is, how much vision it might create. "My idea of success is to take someone who's completely blind and allow them to walk outside unaided," says Dr. Joseph Rizzo, who heads the Mass Eye and Ear retinal team. But despite rivals' more optimistic forecasts, Rizzo and other researchers say such a system is at least a decade away. In the meantime, researchers are contemplating a host of new solutions to age-old medical problems. "The one I'm eager for is a memory pros-thesis [though] it probably won't happen in my lifetime," says Heetderks of NIH. Perhaps not. But people with these afflictions are thankful there are researchers who dare to dream.