Shattered Nerves: How Science Is Solving Modern Medicine's Most Perplexing Problem

10 In the Eye of the Beholder

∑ 10 In the Eye of the Beholder In a small, windowless room chockablock with ophthalmic equipment at the Doheny Eye Institute on the University of Southern California’s Medical Center Campus in Los Angeles, a slight, 76-year-old woman sits in a chair facing a blank wall. Although the room is dark, she is wearing a pair of sunglasses as well as a patch over her left eye. Connie Schoeman is totally blind, yet she is able to tell biomedical engineer Arup Roy whenever she sees a square-shaped light image appear on the wall in front of her. Operating the computer that controls the light display, Roy flashes the image a total of ten times, and Schoeman correctly identifies all but one. She can do so thanks to a minuscule spatula-shaped sliver of plastic containing sixteen round platinum electrodes attached to her retina, the tissue paper–thin membrane that lines the inner wall of the eye. The images Schoeman sees are transmitted to the retinal implant in her eye by a tiny camera mounted on the bridge of her glasses. A wire leads from the camera to a small circular object that sits firmly on her scalp just behind her right ear. It contains a miniature radio transmitter that is held in place by a magnet attracted to a receiver-stimulator implanted in a hollowed-out portion of her skull. Under the skin and musculature of her scalp, a small cable made up of sixteen tiny wires runs from the receiver-stimulator to In the Eye of the Beholder 153 her right eye, where it is attached to the four-by-four electrode array on her retina. Schoeman now readies herself for a more di≈cult test of her neural prosthetic device. As Roy begins this test, a tone chimes periodically. Sometimes the tone is accompanied by the projection of light onto one of four corners of an imaginary square on the wall. Other times, no light accompanies the tone. Schoeman is asked to determine whether the light has come on, and if so to point to its location. With each tone, her head sweeps in exaggerated up-and-down and side-to-side motions as she scans the wall looking for the light. This motion is made necessary by the fact that the electrodes inside her eye o√er no peripheral vision. They are actuated only when the camera on her glasses is aimed precisely at the light. A slight movement one way or the other and they go o√, requiring Connie to immediately turn her head back toward the light. It can be a frustrating exercise, much like an amateur astronomer trying to find a planet or star in the night sky with an inexpensive telescope. The light-in-the-corner test is run in two sets of ten tones. During the first set, Schoeman correctly identifies and locates the light nine out of ten times. During the second, her accuracy falls to six out of ten, perhaps because of fatigue. In previous tests, Schoeman has been able to identify a paper plate, a cup, and a knife, not because they look like what they are to her but by the number and configuration of the points of light she sees when the electrodes in her eye are activated. She was told ahead of time that various white eating utensils were placed in front of her on a black background. She was then asked to identify what they were. ‘‘I know it’s a paper plate because there are more dots of light for the plate than there are for the cup, and the knife has dots going down like in a column,’’ she said. In the case of the plate, she doesn’t see a circle because she does not have enough electrodes in her eye, but she does see dots on either side, much like what a dot matrix printer with only sixteen dots would produce. Even though Schoeman can see only light dots that resemble incandescent bulbs, that is a lot more than the nothingness she saw prior to being implanted with a retinal prosthesis. 154 Shattered Nerves Schoeman was blinded by retinitis pigmentosa, an inherited degenerative disease that a√ects the photoreceptor cells of the retina—the rods and cones. The retina, which processes light, lines the back wall of the eye and is actually an outgrowth of the...