Artificial Retina Project has ORNL roots
Eli Greenbaum’s work with chlorophyll has been a factor in the Artificial Retina Project and in several spin-off technologies.
About a decade ago, Elias Greenbaum, UT-Battelle corporate fellow and leader of ORNL's Molecular Bioscience & Biotechnology Research group, and Mark Humayun, of the University of Southern California's Keck School of Medicine, founded DOE's Artificial Retina program, aimed at restoration of sight to people who are blinded by age-related macular degeneration and retinitis pigmentosa.
"I listened to Mark's presentation on artificial sight at a DARPA (Defense Advance Research Projects Agency) meeting and was impressed with his work. I thought, how can I get involved with this project?" says Eli. "One thing led to another. We started a pilot project collaboration that led to the Department of Energy's Artificial Retina Project."
DARPA's aim was to develop cell-based systems that can identify human health risks in the battlefield and improve the performance of chemical and biological sensors and detectors. To Eli, it was also an opportunity to work with a great retina surgeon to provide partial sight to people who couldn't see.
"Mark and I presented this idea to DOE program managers Drs. Dean Cole and Michael Viola, first as a pilot project and then as a full team proposal with multiple national laboratories, universities and Second Sight Medical Products as the CRADA (cooperative R&D agreement) partner," Eli says.
Retinal diseases such as age-related macular degeneration and retinitis pigmentosa destroy vision by annihilating photo-receptor cells in the eye.
By 2002, a team led by Humayun at USC's Doheny Eye Institute had effectively implanted an array containing 16 microelectrodes into the eye of a patient who had been blind for more than a half-century. Humayun successfully demonstrated that if retinal tissue is stimulated electrically using electrodes implanted in the eyes of legally blind patients, many of these people can perceive image patterns that mimic the effects of stimulation by light.
The Artificial Retina Project branched out beyond ORNL in the late 1990s when the Lawrence Livermore and Sandia national labs stepped forward to fabricate the electrode arrays and integrated circuit chips that are used to actuate the device.
The eventual research team, consisting of six DOE national laboratories, the Jet Propulsion Laboratory, four universities and private industry, developed a retinal device that replaces the eye's lost light-gathering function of the rods and cones with a video camera.
"A miniature camera mounted in eyeglasses, or ‘pho-glasses,' captures images and wirelessly sends the information to a microprocessor," says Eli. "The data is converted to an electronic signal and transmits it to a receiver on the eye."
The receiver is able to transmit signals through a tiny cable to the microelectrode array, emitting pulses. The artificial device bypasses defunct photoreceptor cells and transmits electrical signals straight to the retina's remaining workable cells. The pulses travel to the optic nerve and finally to the brain, which perceives patterns of light and dark spots corresponding to the electrodes stimulated.
Patients learn to interpret these visual patterns. "The vision isn't 20-20, but it's still something, and will improve with additional R&D," says Eli.
One trial patient equipped with a 60-electrode retinal implant describes on the Artificial Retina Project's website how she looked up at a night sky and detected the full moon. As electrode technology progresses, sight would theoretically improve as more electrodes are added to the five-millimeter-square area on the retina than can receive the implants.
The more retinal implants, the better the vision would be for a patient. This simulation shows vision with (from left) 12 electrodes, 200, and more than 1000.
And then there was the spinach factor. Eli and colleagues in the Chemical Sciences Division proposed replacing inactive photoreceptors in a patient's retina with spinach, a special protein, which "generates a voltage in response to light that may prove able to trigger optical signals to the brain," says Eli.
Eli and his coworkers, including Tanya Kuritz and Ida Lee, demonstrated that chlorophyll-containing proteins in spinach give off a small electrical voltage after capturing the energy of incoming photons of light. The same spinach protein could potentially be used to replace key, light-receiving parts of the human eye that have lost their ability to function.
One potential advantage to using the spinach protein would be a more efficient delivery of an electrical signal to the retina. In such a system, because the photo reception is directly into the eye, the camera-equipped glasses would not be necessary. It is also theoretically possible to implant many more proteins into the retinal area than the man-made electrodes, which could improve image resolution.
Eli describes the chlorophyll research as "inspired by Mark Humayun's pioneering work." Spin-off technologies include Aqua-Sentinel, a chem-bio sensing system that can help protect water supplies, and a treatment to prevent blindness from diabetes by supplying oxygen to blood-starved retinal tissues through retinal implants.
Currently, close to 30 people worldwide are testing the Artificial Retina Project implants in clinical trials. The artificial retina won't be a cure-all for blindness: Eli points out that not all patients are alike, and some sufferers of the sight-robbing diseases are affected more severely than others. But he believes that the research project will eventually help many people to see again.
"Everyone is really doing great work," says Eli. "It's just a pleasure to go to the PI meetings and seeing some of the top notch people working on this important research."—Joanna Finney