Vision of the Future
Jens was a 17-year-old nailing down railroad ties when a splinter broke off and punctured his left retina, blinding him in that eye. Three years later, while he was fixing a snowmobile, a splinter of metal broke off from the clutch, destroying his other eye.
Now 39, Jens lives in rural Canada, where he splits and sells firewood, sometimes loading as much as 12,000 pounds a day. He and his wife have eight children, and when he is not working in the forests, he programs computers, tunes pianos and gives an occasional concert.
But he wanted to see again so badly that Jens--he prefers not to have his last name known--recently paid an estimated $115,000 to have surgeons in Portugal drill a hole in his skull and place an array of electrodes on the surface of his brain. The electrodes are connected to a miniature television camera and a sophisticated computer that, together, have given Jens a rudimentary form of vision.
This summer he demonstrated his new sight at a New York meeting by navigating through rooms, finding doors and even driving a car briefly around a parking lot, avoiding a trash bin and other obstacles placed in his path.
“This is pretty crude vision right now, if you want to compare it to what I had before,” Jens said. “But fortunately, there is a good improvement compared to being blind totally.”
Researchers have been struggling for more than two decades to produce some kind of artificial vision for the blind, and they are now on the right track. For now, Jens is one of only a handful of people who have received newly developed treatments to restore vision, and few experts expect the number of recipients to grow rapidly any time soon. But the fact that anyone has been treated at all represents a major technological breakthrough.
Reflecting that newfound optimism, nearly a dozen labs throughout the world are racing furiously toward a common goal--bypassing damaged components of the visual system to restore sight. Some are developing artificial retinas, some are using electrodes to stimulate neural pathways in the eye, and still others are trying to stimulate the brain directly. Few, however, have done much in humans--yet.
“We’re still at a very primitive stage, in the sense of how much work will be required to ... produce enough vision for mobility,” said Dr. William Heetderks of the National Institutes of Health. “It’s very easy to underestimate the technical problems involved.” Although the prosthesis used by Jens is now being marketed to consumers, experts predict that it will be a decade before other devices see much use.
The need for technological breakthroughs has never been greater. According to a recent report from the National Eye Institute, more than 1 million Americans over 40 are blind, and an additional 2.4 million are visually impaired as a result of diabetic retinopathy, age-related macular degeneration, cataracts or glaucoma.
Those numbers are expected to double over the next 30 years as the baby-boom generation ages. New drugs and other therapies are delaying the onset of blindness for many victims, but once blindness sets in, there has traditionally been nothing more that could be done.
Now that situation is changing, as is illustrated by work in three labs that seem to be ahead of the field.
Miniature Electrode Array
At USC’s Doheny Retina Institute, Dr. Mark Humayun and Dr. Eugene de Juan Jr. have developed a miniature electrode array that can be implanted in the eye to replace a damaged retina. The array is attached by thin wires buried under the skin to a radio receiver that is implanted behind the ear.
Visual signals from a video camera are processed through a microcomputer worn on a belt, then transmitted to the receiver. The retinal array stimulates optical nerves, which then carry a signal to the brain. The signal is perceived as phosphenes, bright points of light. With correct stimulation, patterns of phosphenes can draw a picture in the mind similar to that seen on a stadium scoreboard, where letters and pictures are produced by arrays of individual lightbulbs.
The preliminary results have been “encouraging,” Humayun said. “The brain can make a lot of sense out of crude inputs.”
The team has implanted the devices temporarily in 17 patients to date. When they used as few as four electrodes, De Juan said, patients could tell if an object was in front of them, moving from left to right or vice-versa, and so forth. With a four-by-four array of 16 electrodes, patients can see shapes and outlines and pour a liquid from one cup to another.
“To read, we may need 1,000 electrodes,” Humayun said.
In February, the USC researchers performed the first permanent implant of a four-by-four electrode array in a patient, and they plan to do a total of three this year. The device is manufactured by Second Sight LLC of Valencia. Sandia Laboratories is developing second-generation versions of the devices.
The first patient “is doing much better than the patients with the short-term implants--far better than we expected,” Humayun said. The brain, he added, is constantly learning how to interpret the visual signal. “It meets us halfway.”
If the first three implants are successful, De Juan and Humayun have permission from the Food and Drug Administration to implant another seven. But completing the test will take a long time, Humayun cautions, because “it’s a Class III device--the highest-risk device according to the FDA. That’s because it’s an implant that will be left in for the rest of the person’s life.”
Eventually, De Juan said, they would like to shrink the device so that everything would fit into the eyeball. Similar technology is being developed at the Massachusetts Eye and Ear Infirmary in Boston and at the Catholic University of Louvain in Belgium.
Tiny Artificial Retina
Dr. Alan Chow of the University of Illinois at Chicago Medical Center has produced a completely implantable artificial retina, but there are substantial questions about how well it works. Chow and his brother Vincent, president of Optobionics Corp. of Wheaton, Ill., have developed a silicon chip that is 2 millimeters in diameter--smaller than the head of a pin--and half the thickness of a sheet of paper.
The chip contains about 5,000 small solar cells, each attached to a miniature electrode on the back of the chip. The idea is that light falling on the chip will activate the electrodes, stimulating the optical nerves behind the retina. Most critics, such as Heetderks, do not think the solar cells can generate sufficient electrical power to activate the nerves.
Nonetheless, Chow has implanted the devices in six patients. “All of the patients have improved visual function, sometimes quite dramatic,” Chow said.
One patient, for example, had no light perception previously but “can now see people standing in front of her.” Another patient, “who could read no letters on an eye chart, is now reading about 25” letters on the chart.
“We’re pretty excited,” he added. “We hope these improvements persist.”
But Chow concedes that the implant may not be working the way it was designed to. Retina cells that are physically separated from the implant “seem to have improved in function in all the patients,” he said. That suggests that the surgery may have triggered the release of a growth factor or some other chemical in the eye that led to regeneration of retinal cells.
Whatever is happening, Chow plans to implant four more of the devices and monitor the progress of all 10 recipients. “If [the implants] seem to be consistently effective and safe, the study will be expanded to an undetermined number of patients.”
A significant number of the blind, like Jens, have badly damaged optic nerves, however. For them, a simple retinal implant will be of no benefit, and a more invasive procedure is required.
Skull Implants
Electrical engineer William H. Dobelle of the Dobelle Institute in Commack, N.Y., has been attempting to produce such a device for nearly three decades. He has developed a thin array, containing 64 electrodes, that is implanted inside the skull on the surface of the occipital lobe of the brain. There the electrodes directly stimulate the visual cortex. The device is connected to an electrical socket that passes through the skull and skin.
Outside the skull, the device is similar to the retinal stimulators, with a television camera mounted on glasses and a small computer to process the signal. This is the device that Jens wears.
Dobelle’s team has now implanted the devices in eight patients from six countries. One patient, blind from birth in one eye, lost the other at age 45. Another, who was 77 at the time of the surgery, lost both eyes in a mortar attack during World War II. For some of the patients, insurance covered all or part of the cost of the procedure; others paid the full $115,000 themselves.
Because of U.S. Food and Drug Administration restrictions on implanting medical devices in the brain, the surgical procedures were performed at the University of Lisbon Medical School in Portugal. Arrays were planted on each side of the brain.
The implants produced “excellent displays of phosphenes” in all eight of the patients, Dobelle told the New York meeting of the American Society for Artificial Internal Organs, and four of them reported that the phosphenes were brilliantly colored. The devices are primarily designed for mobility rather than reading, Dobelle said. But “rapid advances provide the possibility that the patients will be able to scan the Internet and watch television,” he added.
Implanting the arrays on the brain’s surface creates many problems, however.
A moderately high voltage is required to stimulate the target cells inside the brain, and it is not possible to stimulate small groups of cells specifically. The voltages applied could, in some cases, provoke epileptic seizures.
The National Institutes of Health has thus been sponsoring studies by researchers such as Dr. Richard Normann of the University of Utah and Dr. Phil Troyk of the Illinois Institute of Technology in which the electrode arrays will be implanted in the interior of the brain, directly in contact with the cells to be stimulated.
One key difference is that the voltages required to stimulate the cells will be reduced by a factor of hundreds to thousands. “As a rule of thumb, when something changes by a factor of 10, you are in a different ballpark, and here we are talking about hundreds or thousands,” said NIH’s Heetderks.
“We need to put in structures that are comparable in size to neurons,” Normann said. “And the materials themselves have to be regarded by the brain as not overtly hostile. It’s a challenging problem,” but when they succeed, surgeons will have a tool that can be used to treat not only blindness but also deafness, incontinence, spinal injuries and other problems, he said.
Researchers in all these areas still have a long way to go, but the progress is heartening. In the long run, many researchers believe that electrodes implanted deep within the brain will provide the best results, but the other alternatives may provide benefits to blind people who cannot wait that long.
“I believe that I am safe in saying that Braille, the long cane and the guide dog are doomed to obsolescence,” Dobelle said. “By the end of this century, they will be as obsolete as the airplane made the steamship.”
