From Darkness to Light: Giving Sight to the Blind
Oct. 6, 2000 — Science fiction is becoming less fiction and more fact every day. It is highly possible that in the not-too-distant future, medical science and technology will enable paralyzed people to walk, deaf people to hear, and blind people to see.
For Letitia Dobosy, the innovations can’t come soon enough. When she was 29, she sensed something was wrong. “There was suddenly this imbalance in my eyes,” she tells WebMD. “I was seeing differently out of each eye.”
Her diagnosis: retinitis pigmentosa, a disease that slowly destroys the rods and cones within the eye’s retina — the light-sensitive cells in the back of the eye that make sight possible. In the U.S., retinitis pigmentosa is the leading cause of blindness in young people. That was 15 years ago, and doctors told her she would be blind by now. “But I’m not there yet,” she says.
Still, Dobosy’s interaction with the world has gradually altered as her eyesight has diminished. She can still read regular-sized print but has in recent years faced some limitations. “I gave up driving two years ago,” she says. “I used to sew my own clothes … I’m starting to have issues with mobility especially in unfamiliar territory … problems with depth perception.”
Dobosy says she has tunnel vision. But at present, medicine offers no means to reverse her progressively debilitating condition — the key phrase being “at present.”
While Dobosy’s diagnosis is shared by millions, so too is macular degeneration, a cause of blindness that affects children and adults over age 60. “They are unable to read or drive or recognize faces — or do anything that requires keen vision. They lose their independence because they can’t drive, so they can’t get from place to place, do their own shopping,” says Philip Hessburg, MD, president of the Detroit Institute of Ophthalmology.
They are typically healthy people who find their independence and their lives limited forever by something entirely out of their control. “Once someone has lost all their vision, the options are to learn Braille, to have a reader, or to obtain a leader dog,” says Hessburg.
Blindness — once relatively ignored by research scientists — has in recent years received greater attention and increased funding, all driven by expectations of increasing numbers of cases of blindness in an aging population.
Around the world, “bionic eyes” are under development.
Last summer, Hessburg headed an international symposium that brought together 20 of the world’s leading researchers working on these inventions. The majority, he tells WebMD, are focused on developing intraocular retinal implants — small microprocessor chips embedded in the eye, which send a message through the optic nerve to the brain.
One group of researchers at the Wilmer Eye Institute at Johns Hopkins Medical Center in Baltimore has paired a tiny television camera with something called an ultrasonic distance sensor (mounted on a pair of eyeglasses). The glasses send the signal to the sensor, which sends a signal to a microcomputer chip embedded on top of the retina — which transmits signals to the brain’s visual cortex, the area of the brain that controls vision, explains Giflin Dagnelie, PhD, assistant professor of ophthalmology at John Hopkins Medical School in Baltimore.
When the camera sends a video signal to the small processor, the image is streamlined, says Dagnelie. “It basically pares the image down to the most important components, like edges and contrast — so a person can see the outlines of a face, see a doorway, obstacles in their path, things like that. We think it will be a while before it’s good enough that they can recognize faces with this, but they will be able to distinguish faces.”
In preliminary tests involving six patients — performed under local anesthesia, so patients could report what they were seeing — Dagnelie and colleagues first showed them one or two dots, then as many as 25 dots in a 5- by 5-inch square, then one letter at a time,” he tells WebMD. The images they see are very crude, he adds. “Think of this as a stadium scoreboard, but just a tiny little corner of it made up of big crude dots. It corresponds to about 20/2000 vision — really primitive.”
“We expect that the first implants will be similar to that. It will tell them something about obstacles, enough to get around, enough to see where a person is sitting,” Dagnelie tells WebMD. “To a blind person, that can be a whole lot. And as the technology gets better and as we get better at implanting it … the image will get finer, and we’ll be able to get better resolution. But this is a start.”
Within three to five years, Dagnelie says, he expects patients to have long-term implants that will help them operate more independently. “I expect people will be able to distinguish big letters, possibly read a label or a short piece of text. [But] they won’t be able sit down and read a newspaper, at least not in the near future.”
Another version of a bionic eye being developed by Optobionics in Chicago integrates all components into one chip implanted below the retina of the eye; it’s called the Artificial Silicon Retina. “The design of our chip is relatively simple and may be able to function solely with the power provided by light entering the eye,” says Vincent Chow, an engineer who co-founded Optobionics Corporation.
“Presently, our chip does not require connecting wires, batteries, or other [outside] devices,” says Chow. “The artificial silicon retina is made up of thousands of microscopic solar cells that convert light into electrical impulses and is capable of electrically stimulating [the] remaining cells in the retina when implanted [into the eye].”
“What a patient sees will greatly depend on how the microscopic solar cells on the chip interact with the remaining functional retinal cells,” Chow tells WebMD.
This summer, three patients received implants as part of the first multimonth study of any retinal implant. While Chow declines to report the degree of vision patients have experienced, he says that there have been no signs of rejection or other complications, and that preliminary results will be announced soon. Chow invented the artificial silicon retina with his brother, Alan Y. Chow, MD, a visiting professor at the University of Illinois in Chicago and clinical assistant professor of ophthalmology at Tulane University Medical Center in New Orleans.
Yet another development under way at various institutions — the Dobelle Institute in New York, the University of Utah, and the Kresge Eye Institute in Detroit — focuses on creating a new cornea or eye altogether by using some of the mechanics already mentioned but then bypassing the eye entirely.
One version, the Dobelle Eye, consists of a subminiature television camera and an ultrasonic distance sensor, both mounted on a pair of eyeglasses. The sensors connect through a cable to a miniature computer, which is worn in a pack on a person’s belt. The computer then sends impulses to electrodes that were implanted directly into the patient’s visual cortex area in the brain. In one report, a 62-year-old man blinded in an accident was able to read 2-inch-tall letters at a distance of 5 feet — enough to help him navigate in unfamiliar environments.
All the developments have merit, says Hessburg. Whichever proves to be the most viable option, they all show that there is hope on the horizon. “I believe there will probably be useful implants within the next five years, but my scientific guess is that implants which would allow somebody to read the printed page are probably 25 to 50 years away,” he says.
“I think it’s possible, probable, and I believe it will occur. I’ve been working in the field of ophthalmology since … 1964, and I’ve always dreamed this was possible. It’s only in the past decade that I have believed that it is probable,” Hessburg tells WebMD.
His center has “the largest support groups in the U.S. for visually impaired adults,” he tells WebMD. “They have hope, and it isn’t false hope. We’ve talked to them realistically. But the question is, how fast can science move? It’s not going to be solved by one university all of a sudden having a light-bulb idea. It’s a huge problem in blending electronic mechanisms with biological mechanisms and ending up with a sophisticated output.”
“Retinal implants are worthy of investigation, and may turn out to be the answer, but it’s been slow in coming,” Paul Sternberg, MD, Thomas Aaberg professor of Ophthalmology and director of the retina service at Emory University School of Medicine in Atlanta, tells WebMD. “We’ve been telling patients for six years and more that it will be along any day. You get to the point where you want to give them something more definite.
“To be truthful, I think that the corneal devices — those that create a whole new eye of sorts — show the most promise. Maybe it’s best to leave the damaged eyes alone and start over.”
Retinal gene therapy, retinal transplantation, neuroregenerative drugs — growth factors that can stimulate regeneration of retinal tissue — also give hope to cures for blindness, Sternberg adds.