LASIK Eye Surgery
Medical Author: J. Bradley Randleman, MD
Coauthor: John F. Payne, MD
Medical Editor: Melissa Conrad Stöppler, MD
What is LASIK?
LASIK stands for laser in situ keratomileusis, which means
using a laser underneath a corneal flap (in situ) to reshape the cornea (keratomileusis).
This procedure utilizes a highly specialized laser (excimer laser) designed to
treat refractive errors, improve vision, and reduce or eliminate the need for
glasses or contact lenses. This laser procedure alters the shape of the cornea,
which is the transparent front covering of the eye. Though the excimer laser had
been used for many years before, the development of LASIK is generally credited
to Ioannis Pallikaris from Greece around 1991.
How does LASIK work?
During the LASIK procedure, a specially trained eye
surgeon first creates a precise, thin hinged corneal flap using a microkeratome.
The surgeon then pulls back the flap to expose the underlying corneal tissue,
and then the excimer laser ablates (reshapes) the cornea in a unique
pre-specified pattern for each patient. The flap is then gently repositioned
onto the underlying cornea without sutures.
What is refractive error?
In the human eye, the front surface (cornea) and
lens inside the eye form the eye's "focusing system" and are primarily
responsible for focusing incoming light rays onto the surface of the retina,
much like the lenses of a camera focus light onto the film. In a perfect optical
system, the power of the cornea and lens are perfectly matched with the length
of the eye and images are in focus; any mismatch in this system is called a
refractive error, and the result is a blurred image at some location.
What are the primary types of refractive error?
Myopia (nearsightedness): In people with myopia, the mismatch in focusing
power and eye length causes distant objects to be blurry and near objects to be
clearer.
Hyperopia (farsightedness): In people with hyperopia, the mismatch in
focusing power and eye length causes near objects to be blurry and distant
objects to be relatively clearer.
Astigmatism: In people with astigmatism,
either the corneal or lens shape is distorted, causing multiple images on the
retina. This causes objects at all distances to appear blurry. Many people have
a combination of either myopia or hyperopia with astigmatism.
How do glasses or contacts improve vision in people with refractive errors?
Glasses or contact lenses are used to compensate for the eye's refractive error
by bending light rays in a way that complements the eye's specific refractive
error. In contrast, LASIK and other forms of refractive surgery are intended to
correct the eye's refractive error to reduce the need for other visual aids.
Next: What happens to vision when we age? »
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Last Editorial Review: 9/14/2007
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