When she was 42, toxic optic neuropathy destroyed the bundles of nerves that connect Gómez’s eyes to her brain, rendering her totally without sight. She’s unable even to detect light.
But after 16 years of darkness, Gómez was given a six-month window during which she could see a very low-resolution semblance of the world represented by glowing white-yellow dots and shapes. This was possible thanks to a modified pair of glasses, blacked out and fitted with a tiny camera. The contraption is hooked up to a computer that processes a live video feed, turning it into electronic signals. A cable suspended from the ceiling links the system to a port embedded in the back of Gómez’s skull that is wired to a 100-electrode implant in the visual cortex in the rear of her brain.
Much earlier research attempted to restore vision by creating an artificial eye or retina. It worked, but the vast majority of blind people, like Gómez, have damage to the nerve system connecting the retina to the back of the brain. An artificial eye won’t solve their blindness. That’s why in 2015, the company Second Sight, which received approval to sell an artificial retina in Europe in 2011—and in the US in 2013—for a rare disease called retinitis pigmentosa, switched two decades of work away from the retina to the cortex. (Second Sight says slightly more than 350 people are using its Argus II retinal implant.)
“Berna was our first patient, but over the next couple of years we will install implants in five more blind people,”
Her experiment took courage. It required brain surgery on an otherwise healthy body—always a risky procedure—to install the implant. And then again to remove it six months later, since the prosthesis isn’t approved for longer-term use.
Fernandez takes human retinas from people who have recently died, hooks the retinas up to electrodes, exposes them to light, and measures what hits the electrodes. (His lab has a close relationship with the local hospital, which sometimes calls in the middle of the night when an organ donor dies. A human retina can be kept alive for only about seven hours.) His team also uses machine learning to match the retina’s electrical output to simple visual inputs, which helps them write software to mimic the process automatically.
The next step is taking this signal and delivering it to the brain. In the prosthesis Fernandez built for Gómez, a cabled connection runs to a common neuro-implant known as a Utah array, which is just smaller than the raised tip on the positive end of a AAA battery. Protruding from the implant are 100 tiny electrode spikes, each about a millimeter tall—together they look like a miniature bed of nails. Each electrode can deliver a current to between one and four neurons. When the implant is inserted, the electrodes pierce the surface of the brain; when it’s removed, 100 tiny droplets of blood form in the holes.
Fernandez had to calibrate one electrode at a time, sending it increasingly strong currents until Gómez noted when and where she saw a phosphene. Getting all 100 electrodes dialed in took more than a month.
The big downside to the prosthesis—and the primary reason Gómez couldn’t keep hers beyond six months—is that nobody knows how long the electrodes can last without degrading either the implant or the user’s brain