The electrodes stimulate the eye in different patterns multiple times per second, creating flashes of light that correspond to the low-resolution video feed. Essentially, the electrodes take the place of the photoreceptor cells in a healthy eye that respond to light and send information up the optic nerve to the brain.

Second Sight began with a flash of light. In 1991, Robert Greenberg, an electrical engineer turned medical student, stood in an operating room watching as a retinal surgeon inserted a tiny wire into the eye of a blind patient, who was awake and under local anesthesia. When the wire touched the patient's retina and delivered a minuscule jolt of electric current, the man reported a spot of light in his pitch-black field of vision. The surgeon inserted a second wire, and the man saw two spots of light. "If you can create two spots, it seemed obvious to me that you could do a lot of spots and create images,"