June 19, 2003 – For more than 40 million people around the world, blindness is a fact of life. But for the many millions who are afflicted with progressive eye diseases and disorders, restored vision one day may be found in tiny chips implanted in the eye.
Called retinal prosthetics, these devices stimulate the optic nerve that links the eye and brain. The prosthetics may be useful for patients with macular degeneration, an age-related disease that causes severe blind spots, or retinitis pigmentosa, an inherited disorder that affects night vision and peripheral vision.
The $5 million annual industry is expected to grow, thanks to recent successful human trials. Several companies, universities and government laboratories are working on sight restoration systems using MEMS and microelectronics.
Leading the pack is a team from five national laboratories, two universities, and one company developing a MEMS electrode system for people with retinal disorders. The Department of Energy, which oversees the national labs, committed $9 million over the next three years to fund the Artificial Retina project.
In May, researchers presented results from the first phase of testing on three volunteers. Dr. Mark Humayun, founder of the Intraocular Retinal Prosthesis Group at the Doheny Retina Institute in Los Angeles and originator of the project, said the implant partially restored the vision of the blind volunteers. One patient was even able to distinguish between two different objects.
The implant, a chip containing 16 electrodes and measuring 4 millimeters by 5 millimeters, receives signals from a video camera mounted on a pair of glasses. The chip itself is surgically implanted in the eye and covers the retina, electrically stimulating the patient’s functional retinal cells. Second Sight LLC in Sylmar, Calif., manufactures the chips.
With 16 electrodes, volunteers are able to see only very rough shapes, but researchers hope eventually to increase the number of electrodes to 1,000. Humayun said they expect to offer a 60- or 100-electrode chip prototype within two years. Such a chip could restore mobility to blind people, while 1,000 electrodes would be enough to allow patients to read large type.
“The brain has the incredible ability to fill in gaps, by interpolating and morphing to determine low resolution images,” Humayun said. Because the chip uses visual data from a video camera or other external system, there are possibilities for not only improving but also augmenting vision through zooming or color correction, for instance.
Advanced Medical Electronics Corp. (AME) in Minneapolis developed a vision system that relies on heat detection to determine shapes. It uses infrared thermal detectors called microbolometers, which typically absorb radiation, convert it to heat and sense the temperature change. Gary Havey, president of AME, said the devices could be used to send a signal to implants.
“Some time ago we recognized that infrared would have advantages for blind people,” Havey said. Microbolometers have the advantages of being low cost, mass producible and compatible with low-resolution implants. AME has received about $500,000 in grants from the National Eye Institute and the National Institutes of Health to develop the technology.
While the DOE’s artificial retina depends on external systems for input, a Saratoga, Calif.-based company called VisionCare has developed a miniature implantable telescope that can project a magnified image over a large area of the retina. Designed for patients with macular degeneration, which damages the center of the retina and creates a large blind spot in the field of vision, the telescope sends light to undamaged portions of the retina. It’s been tested on more than 100 patients around the world.
Another implant company, Optobionics, makes an “artificial silicon retina,” a microchip with 5,000 solar cells that stimulates healthy remaining retinal cells. Six visually impaired people have received the Optobionics chip so far, and they report the ability to perceive light and make out shapes.
Dr. Bill Dobelle of the Dobelle Institute in Lisbon, Portugal, claims there is hope for people who have lost all functionality in their retina, too. He designed a system that includes a video camera, external signal processing equipment, and a brain implant that gives blind people with totally non-functional retinas the ability to make out patterns of light, navigate through houses, and in highly controlled environments, even drive a car.
Thirteen patients have received implants to date. Dobelle is working on an upgrade that will incorporate more electrodes to improve resolution.