IMPROVED techniques for corrective laser eye surgery could give
people much better eyesight than those with so-called normal
vision, say researchers in the US. Jim Schwiegerling, an
ophthalmologist at the University of Arizona in Tucson, says
customised surgery could take patients to the theoretical limits
of human vision. People would be able to pick out small objects
from twice or maybe even four times as far away as those with
normal or 20/20 vision. Fewer than 5 per cent of people are born
with such super-vision. Poor eyesight is caused not only by
short and long-sightedness, but by asymmetries in the cornea and
lens that distort images. But at the moment, laser surgery on
the cornea corrects only major aberrations such as the
cylindrical errors that cause astigmatism or the spherical
errors that cause "defocus". In fact, the surgery can actually
introduce new aberrations. "With standard treatment you are
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