Electrical eye implant offers hope
February 21, 2005
Gianluca Lazzi is an electrical engineer at N.C. State University, but he can fill a blackboard with detailed sketches of the human eye.
His drawings reveal the complexities of retinas, optic nerves and photoreceptor cells -- and how he and others are on the verge of reversing blindness by using electrical implants.
"At the end of the day, everything in our body is electrical," Lazzi said. "I know that from study. But when I think what we are doing, it really is incredible."
Lazzi is part of a national team of engineers, scientists and surgeons who have created an artificial retina. Since 2002, six patients who had lost their sight can now "see" with the help of cameras and transmitters that relay signals to electrodes implanted in the eye.
While the images hardly replicate normal vision, the results suggest that certain types of blindness once considered incurable can now be partially reversed.
"I don't want people to think I can see like I used to," said Harold Churchey, 77, who lives in northern Maryland. "But I can see light, and under the right conditions, I can scan the shapes of things. To see something when you couldn't see anything, well that has to be positive."
Churchey lost his sight in the mid-1980s to retinitis pigmentosa. People with the disease, as well as those who have macular degeneration, are good candidates for the artificial retina.
About 9 million Americans, most of them older, have been diagnosed with one disease or the other. Almost 2 million of them have little or no vision.
Both diseases cause a loss of vision because photoreceptor cells die off inside the retina. Those cells translate light into electrical signals that the brain interprets as images.
In theory, the goal of the artificial retina is easy to grasp. It's designed to replace photoreceptor cells with electrodes produced in a lab.
But turning that theory into practice teeters on the brink of science fiction.
Complex path to vision
Led by the U.S. Department of Energy's Office of Science, a team of five DOE labs, a private company, NCSU and two other universities re-create vision starting with a small digital camera attached to a patient's glasses.
Images captured by the camera are processed through a device patients wear on their belts, which then transmits signals to an antenna implanted in the eye. The signal is processed one more time on its way to a small grid of electrodes that perform the task formerly done by the photoreceptors.
"This is all done on a scale that is incredibly small," Lazzi said. "And the electronics are immersed, basically, in salt water -- saline -- which is very harsh on the electronics."
Sitting in his office at NCSU's Centennial Campus, Lazzi pulls a sealable plastic bag from his desk. It's full of prototypes used in past experiments -- tiny antennas, transmitters and circuits. He calls it his "petting zoo."
A grid about 5 millimeters by 5 millimeters, small enough to sit on the tip of a pinkie finger, falls to the desk.
It's this kind of grid that's implanted on the inside wall of the retina -- the part of the eye that has the nerves that sense light and the blood supply that nourishes those nerves. The retina is fragile, with the consistency and thickness of wet tissue paper, making implantation of the device difficult.
Lazzi's design contains 16 electrodes -- four down and four across. It's much better than some of the earliest prototypes, but not nearly compact enough.
With 16 electrodes, the image from the camera is incomplete and boxy. Churchey, the patient, can distinguish a cup from a plate if the objects are white and the background is black. But he doesn't see the whole cup or the entire plate at once.
"What I do is move the camera until I find the edge of the plate, and then I scan across until I figure out the shape," he said.
More detail will require more electrodes -- many more. Lazzi is working on grids that will hold 256 electrodes. The goal is a grid with more than 1,000 electrodes by the year 2013. Those grids should produce images that allow patients to see far more detail.
But electrical circuits produce heat -- and too much heat will scar the retina.
"And if you damage the retina, you're done," Lazzi said. "You failed."
Competition in sight
Doctors who aren't involved in the Energy Department project praise its work but said people need to understand that the breakthrough is in its early stages.
"We are watching with fascination," said Dr. Cynthia Toth, an associate professor of ophthalmology at Duke Eye Center who performs a surgical procedure to prevent blindness in patients with macular degeneration. "Everyone realizes that it is easier to attack a disease early on, but we see many people who are out of options. This offers something."
It's also possible that someone else could produce a better device before 2013.
Several groups from Japan, Germany, Portugal and the United States are working on products with designs similar to the one used by the DOE project, said Dr. Tim Schoen of the Foundation Fighting Blindness. And scientists involved in stem cell research are working toward the same goal using entirely different means.
"One of these groups is going to emerge a winner," said Schoen, whose foundation works with researchers around the world. "It's a bit like the early days of the cochlear implant, only more complex. But when they finally figure it out, the real winner is going to be the patient."
Churchey already appreciates what science has done for him. He will never see well enough to drive a car again or read a book, but he can find his way around a room. He can look out a window and know it's a sunny day.
And later, something more important will happen.
"I know some day because of me," he said, "a child will see."