THINK you鈥檝e got perfect vision? Think again. Pablo Artal reckons he can
double the sharpness of anybody鈥檚 vision, no matter how good it is to start
with. He revealed his 鈥渟mart spectacles鈥� technology at a conference on adaptive
optics in Murcia, Spain, last week.
Few people would choose to wear Artal鈥檚 prototype, as the computer hardware
it relies on takes up a full square metre of desk space. 鈥淏ut the key optical
component is very small and cheap,鈥� says Artal, a researcher in the optics
laboratory at the University of Murcia.
Conventional spectacles correct for poor focusing and astigmatism in the
eye鈥檚 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.
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In adaptive optics, light from a star, say, 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鈥檚 spectacles do the same thing for transient
imperfections in the eye, correcting for them 25 times every second. 鈥淓verything
sharpens up as you switch on,鈥� 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鈥檚 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鈥檚 lens and tells the mirror chip to deform the mirror in real time
(see Diagram).
Because light reaches the user鈥檚 eyes via the deformable mirror, the
computer can ensure that the user sees a perfect image.
The mirror鈥檚 shape is updated 25 times per second鈥攁bout 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 at a range of 12 metres
objects so small that someone with 20:20 vision can鈥檛 see them farther away than
6 metres. But Fred Fitzke, an ophthalmologist at University College London, is
more cautious: 鈥淎t the moment, we don鈥檛 know what other limits there are to
vision鈥攍ike 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.鈥�
As well as having possible military applications, the super specs can be used
in reverse to take real-time precision images of the retina. 鈥淵ou can use it to
take microscopic images of individual cells and diagnose eye diseases very
early,鈥� says Austin Roorda of the University of Houston.