11 June 2000
Technology Makes 'Super' Human Vision Possible
by Kate Melville
Adapting technology originally developed by astronomers to obtain better images of the heavens, a University of Rochester scientist has developed an optical system that has given research subjects an unprecedented quality of eyesight. The research dramatically improves the sight even of people who have 20/20 vision. Vision scientist David Williams presented his work this week at the summer meeting of the American Astronomical Society in Rochester, N.Y.
While the work is still in a research stage, eye-care giant Bausch & Lomb has licensed the technology and is working with University researchers to commercialize it.
"For years David has been way out in front exploring how we could enhance people's vision beyond what is normally thought of as perfect vision," says Scott MacRae, one of the world's leading cornea specialists and a widely recognized pioneer in refractive surgery. MacRae is moving to the University's Medical Center this month to join Williams at the newly established Alliance for Vision Excellence, a new collaboration between the University and Bausch & Lomb that is dedicated to improving technology to correct vision-impairing anomalies of the eye.
"In the old days," says MacRae, "we were just trying to correct people's vision problems and treat disease. This new research takes what we consider normal vision and enhances it. This is truly revolutionary," says MacRae, who is writing a book on such research, which he calls "the quest for super vision." Just last month at the annual meeting of the Association for Research in Vision and Ophthalmology, researchers from several laboratories and companies devoted a whole symposium to the topic of enhanced vision.
Williams uses technology known as adaptive optics, which was originally developed by astronomers to sharpen images from telescopes by correcting for aberrations in the atmosphere. Adaptive optics have been implemented on several telescopes, including the giant Keck Telescope in Hawaii, resulting in remarkably crisp images. Williams, who is Allyn Professor of Medical Optics and director of the University's Center for Visual Science, has led a decade-long effort to apply the technology to improve ordinary human vision.
His researchers direct a harmless, highly focused spot of light into the eye of a research subject and measure the light that is reflected outward. That light provides a glimpse or snapshot of the topography of the eye in exquisite detail. The light is broken up into 217 laser beams that are sent into a sophisticated device known as a wavefront sensor. The sensor analyzes deviations in each beam's path, revealing tiny imperfections or aberrations that exist in the person's cornea and lens.
The system detects visual distortions so subtle that physicians didn't even know they existed until Williams' laboratory invented the system. Today a visit to the eye doctor focuses mainly on two types of aberration: astigmatism and defocus. Most prescriptions are intended to correct for these two defects. Williams' system can measure up to 65 different aberrations.
These precise measurements are sent to a sensitive "deformable" mirror -- a mirror that can bend and customize its shape according to the measurements of a person's eye. Such flexible mirrors form the heart of traditional adaptive-optics systems used in astronomy. The mirror in Williams' laboratory is a two-inch-wide device that bends as little as one or two micrometers (just one-fiftieth the width of a human hair) thanks to 37 tiny computer-controlled pistons. This subtle shaping, done in response to the customized measurements of a person's optical system, alters the light in such a way that it exactly counters the specific distortions in a person's eye.
In the laboratory, Williams' team has shown that correcting these imperfections can result in greatly improved vision. He has published this work in the Journal of the Optical Society of America.
"When you look through an adaptive optics device, the world looks crisper," Williams says. "In some people, the ability to pick up contrast, such as minute patterns of stripes, is increased by a factor of six. It allows for a level of vision correction that's just not available today.
"It's like needing glasses and getting them for the first time. Everything suddenly looks sharper and clearer, no matter how good your eyes are normally. When you're using the adaptive optics system, you just say 'wow.' "
Williams is an expert on the circuitry of the human retina and the optics of the eye. After discovering some of the basic limits of the optical system of the human eye, he began exploring ways to improve ordinary human vision, eventually working closely with astronomers and other adaptive-optics experts. The research is now funded by the National Science Foundation Center for Adaptive Optics (based at the University of California, Santa Cruz), the National Eye Institute, and Bausch & Lomb.
Williams has found that the visual acuity of the human eye can be somewhere around 20/10. While adaptive optics may someday help patients approach that level, he says that acuity isn't the most noticeable improvement. Adaptive optics improves eyesight most under low-light conditions, such as night-time driving. MacRae, the laser surgery expert, estimates that a driver sharing the road with a bicyclist at dusk could see the bicyclist from roughly twice as far away if he or she were equipped with adaptive optics correction.
In the past, Williams has used the system to look into the eye. In a series of papers in such journals as Nature, Williams' team has published the best images ever obtained of the living human retina. Last year the team was able to differentiate the three types of cones in the living human retina. Detailed information of the eye is helpful to ophthalmologists monitoring patients with diseases like age-related macular degeneration or diabetic retinopathy.
While the current set-up is too bulky to bring the experience of enhanced vision or super vision to many patients, MacRae is confident that that day is not too far off.
"Someday you may no longer have to sit and answer patiently when you're asked repeatedly whether lens No. 1 or lens No. 2 is better," MacRae says. "Someday you may just look into a wavefront sensor as David has developed, and in one quick second we'll have all the information needed to improve someone's vision dramatically."