Eyes like a hawk
New Scientist: 25 November 2000
Eugenie Samuel; Magazine issue 2266
One day your optician could give you superhuman eyesight.
THINK you've got perfect vision? Think again. Pablo Artal reckons he can double the sharpness of anybody's vision, no matter how good it is to start with. He revealed his "smart spectacles" technology at a conference on adaptive optics in Murcia, Spain, last week.
Few people would choose to wear Artal's prototype, as the computer hardware it relies on takes up a full square meter of desk space. "But the key optical component is very small and cheap," says Artal, a researcher in the optics laboratory at the University of Murcia.
Schematic of "smart spectacles" lens technology: All they have to do is make it small enough and light enough to wear as a spectacles frame ...
Conventional spectacles correct for poor focusing and astigmatism in the eye's lens. But almost everyone has subtle additional faults which vary as their pupils dilate and their eyes focus. To try and correct for these problems, Artal and his colleagues turned to the techniques of adaptive optics, which are more commonly used in telescopes and spy satellites.
Pablo Artal, 2005. Source: http://www.harnessinglight.org/artal.htmThere are three discernible uses for adaptive optics: One is to increase the resolution of ophthalmoscopes, in order to see more detail of the retina; the second is the possibility to improve vision--and finally the ability to perform new experiments in vision research with purposely manipulated (but not corrected) optical aberrations.
In adaptive optics, light from a star (typically) is bounced off a mirror which changes shape to compensate for the distortions introduced by fluctuations in the atmosphere. It is these fluctuations in the density of the atmosphere that make stars twinkle. Artal's spectacles do the same thing for transient imperfections in the eye, correcting for them 25 times every second. "Everything sharpens up as you switch on," he says.
In his prototype spectacles, a low-intensity infrared laser beam bounces off the back of the retina and into a sensor via a deformable mirrored membrane. The membrane's shape is controlled by an electric field created by a microchip underneath it.
A computer works out how much the infrared beam has been distorted by the eye's lens and tells the mirror chip to deform the mirror in real time (see Diagram). Because light reaches the user's eyes via the deformable mirror, the computer can ensure that the user sees a perfect image.
The mirror's shape is updated 25 times per second--about 5 times faster than aberrations vary in the eye, so the wearer is unaware of the moving mirror.
Artal says that someone wearing the new specs can see small objects at a range of 12 meters that someone with 20/20 vision cannot see, even from as close as only 6 meters. But Fred Fitzke, an ophthalmologist at University College London, is more cautious: "At the moment, we don't know what other limits there are to vision--like the structure of photoreceptors in the eye, or whether the brain can even use the extra information. But I look forward to finding out with this kind of device."
As well as having possible military applications, the super specs can be used in reverse to take real-time precision images of the retina. "You can use it to take microscopic images of individual cells and diagnose eye diseases very early," says Austin Roorda of the University of Houston.
For more:
Optics Express (2006): Adaptive optics with a magnetic deformable mirror: applications in the human eye
Journal of Vision (2004): Neural compensation for the eye’s optical aberrations
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