Chris James and Robin Millar of the United Kingdom both lost their vision after birth because of a genetic condition known as retinitis pigmentosa, in which light-sensitive cells in the eye stop working. Now, surgeons have partially restored vision to both men with tiny electronic chips that promise to help the blind see the same way cochlear implants have helped the deaf hear. Teams of doctors at the Oxford Eye Hospital and King's College Hospital in London embedded the small square chips—0.12 by 0.12 inches—in a thin sheet of tissue at the backs of the men's eyes. As soon as they were switched on, the chips began performing the duties of defunct photoreceptors—also called rods and cones—converting light into electrical impulses that travel to the brain. A thin cable threaded beneath the skin connects the chip to a battery pack, which also sits under the skin near the ear.

Chris James told the BBC that "there was a 'magic moment' when the implant was switched on for the first time and he saw flashing lights." James and Millar must now learn to interpret the patchwork of bright and dark spots they see in order to recognize people and objects in the world around them. So far, James says he distinguish the outlines of nearby objects.

Retina Implant AG, a medical technology company in Germany, designed the chips that James and Millar received; surgeons have implanted similar chips in at least 10 other patients so far as part of clinical trials. Eberhart Zrenner of the University of Tubingen, who helped found Retina Implant AG, has been improving the chips over the past decade, making them safer and more portable. In a special report on "Tomorrow's Medicine" in the May issue of Scientific American, I wrote about Zrenner's research and a Finnish man named Miikka Terho who also went blind because of retinitis pigmentosa. In 2008, Terho received an earlier version of Zrenner's chip:

"Miikka Terho knows the difference between an apple and a banana. He can tell you that one is round and sweet and crunches when you bite it and that the other is long and curved and turns to mush if you let it ripen too long. But if you ask him to tell one fruit from the other without touching, smelling or tasting them, he is at a loss. Terho is completely blind. For three months in 2008, however, he recovered the ability to distinguish an apple and banana by sight thanks to a tiny electronic chip that researchers implanted in his left eye. Though brief, the new technology's initial success has permanently changed the prospects for Terho and many others like him."

When Terho recognized the fruit as part of a laboratory test of the implant, everyone in the room burst into applause and celebratory laughter. The researchers captured the triumphant moment on video:

Current retinal implants cannot help people with glaucoma or other conditions that degrade the optic nerve. And the chips do not offer the blind crisp and colorful images. Rather, they open small, veiled windows on the world, as though one were looking at silhouettes behind a sheer curtain. But the ability to identify food, tools and sometimes people's faces by sight—even if the images are blurry or indistinct—is a huge improvement over complete blindness.

Retina Implant AG is not the only company engineering retinal implants. California-based Second Sight has also achieved remarkable results by combining an implant with a miniature camera mounted on a pair of glasses. All the recent successes suggest that affordable retinal implants should be available in just a few years. Retinitis pigmentosa and similar conditions have been long been defined as "incurable." Clearly, medical textbooks are due for an update.