The BBC news camera frames a woman in sunglasses, standing on an outdoor basketball court with her grandson. She looks up at the basket, steadies herself, shoots and hits the rim. Just a shot or two later, she banks one right off the backboard.
It might seem odd that an international news team considered this mundane, suburban-America moment worth filming. With context, however, it’s a scene guaranteed to send a shiver down even the stiffest of spines. After all, the woman on the screen is blind. And that shot she made – nailed, really – was made courtesy of an electrode-studded sliver of silicone and platinum implanted on her retina and hooked up to a tiny camera mounted on her sunglasses.
The system was designed and implanted by a team led by Mark S. Humayun, M.D., Ph.D., professor of ophthalmology, cell and neurobiology, and biomedical engineering at the Keck School of Medicine of USC, the USC Doheny Eye Institute and the USC Viterbi School of Engineering, in collaboration with scientists at Second Sight Medical Products Inc.
That basketball shot is testimony to the success of one of the world’s first artificial retinas, and to the drive and passion of the team of ophthalmologists, biomedical engineers, neurologists, materials scientists and others who made it possible.
Ten subjects at four sites have been recruited for a three-year, Food and Drug Administration-approved trial of the second generation of this system – the Argus II Retinal Prosthesis. Work is being done on future, more advanced generations of the implant, as well as on creating a version of the camera that can actually fit inside the eye. The Argus II trials continue in Mexico and are expanding into Europe. |
“The pioneering efforts of the individuals who participate in this clinical trial will lead to advances for the many people in the world afflicted with blindness,” Humayun says.
The Hundred-Eyed Giant Approximately six years ago Humayun headed the surgical team that implanted the very first retinal prosthesis into a patient. Between 2002 and 2004, the Argus I (in Greek mythology, Argus was an all-seeing giant with a hundred eyes) was implanted into six people whose vision had been destroyed by retinitis pigmentosa (RP), a group of degenerative diseases of the retina. RP affects approximately 200,000 people in the United States.
The device ultimately may also be used for millions of people suffering from age-related macular degeneration, or AMD. Both AMD and RP destroy vision by annihilating the retinal photoreceptors that allow light to be translated into recognizable images.
The retinal prosthesis attempts to recreate some of the signals lost when retinal cells die. The camera on the glasses sends visual information to an implanted electronic receiver, which processes the information and passes it along as an electrical signal to the implant’s electrodes. The electrodes, in turn, stimulate the eye’s unharmed nerve retinal ganglion cells, which in turn transmit their own signals through the optic nerve to the part of the brain known as the visual cortex. From these nerve impulses the brain creates its visual picture.
The Argus I implant, which is based on the cochlear implant technology that has helped so many deaf people to regain at least part of their hearing, has to be implanted behind the ear, far from the eye itself. The surgery to put the implant in place required three surgeons, six hours, and a pretty significant recovery time. |
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The Argus II is about a fifth the size of the original. The implant now sits on the surface of the eyeball itself, very close to the electrodes it needs to stimulate. The entire system now can be surgically implanted in just two hours by a single surgeon, with a reduced recovery time for the patient.
“It really is a feat of engineering,” Humayun says.
While the first generation of implants contained 16 electrodes laid out on an array, the Argus II is designed with 60 electrodes to allow for higher-resolution images. Hopes are high that the Argus II will leave its predecessor in the visual dust. The hope, says Humayun, is that the Argus II will increase the ability to walk through a room, navigate pieces of furniture, and find a door or window.
“They’re not going to be reading menus with the Argus II,” says James D. Weiland, Ph.D., associate professor of ophthalmology and biomedical engineering at the Keck and Viterbi schools, who coordinates engineering activities for the retinal implant project. “But we do expect some enhanced orientation and mobility. We do expect that their visual acuity will be improved.”
Humayun adds, “How much better this one is compared to Argus I remains to be seen. We have to wait until we start getting patient data, and for the brain to get used to the device.”
The Ultimate Computer The brain is a wild card, constantly shifting in its response to video input, and constantly learning from what has come before. This learning curve, this brain plasticity, made all the difference in the Argus I testing. “They can see a lot more than we ever thought they would see,” Humayun says. “They can find doors, avoid objects like chairs and tables, even follow the motion on a soccer field. The Argus II will hopefully be that much better, but testing is just really starting with them.”
Not content to stop there, Humayun and his team are working already on the next device, as part of the U.S. Department of Energy’s artificial retina project. That implant, which will have “somewhere in the range of 200 to 300 electrodes,” Humayun says, “is coming along nicely.”
Perhaps even more tantalizing is the prospect of shifting the video camera from a glasses-mounted system to one that would sit right inside the eye, replacing the eye’s crystalline lens. This camera would take advantage of its proximity to the cornea, using that tissue as one of its lenses just as the eye normally does, says Armand R. Tanguay Jr., Ph.D., professor of electrical engineering, biomedical engineering, and chemical engineering and materials science at the Viterbi School and professor of neuroscience at the USC College of Letters, Arts and Sciences.
Tanguay, who heads the team building this device, says that the success of the camera will lie in its miniaturization. “We thought we could build something the size of a Tylenol tablet,” he says. “And we did. Now we’re trying to build one that’s a third of the size of a Tic Tac. It’s a fairly radical design, but I think we have a good chance to achieve it.”
The potential advantages of this internal camera are impressive. With the glasses-mounted system, the only way to look around your environment is to move your head. This not only can create a jerky, almost dizzying image, but it also means that any time you move your head what you are seeing changes. And if you move your eyes but not your head, the image you’re seeing will not change, though your brain may think you’re looking elsewhere.
The internal camera, on the other hand, would move with the eye, tracking vision just the way the eye normally does, notes Tanguay, allowing for the natural coupling of head and eye movements. In addition, it would remove the requirement for the wearer to have a pair of glasses on at all times in order to see. Not only would these people no longer be completely blind, but they would no longer look blind, either.
“Blind people seem to feel that that’s really important,” he says. “They say, ‘Don’t make me look like a geek.’” Weiland adds, “We’ve got this nice piece of hardware. Now we need to figure out how we can program it to provide the most information possible to the
person, to create the most effective perception for that person. It’s a really complex interaction that we have yet to fully understand.”
The Argus II trial and the development of next-generation devices are being supported by the Department of Energy Office of Sciences, the National Science Foundation, the National Eye Institute, Research to Prevent Blindness, the W.M. Keck Foundation and the Albaugh Family Trust. |
