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The laser used in PRK and LASIK is an excimer
laser, one of many different varieties of lasers used for
different types of eye surgery. The excimer laser is a "cold"
laser, meaning it does not produce its effect by heat, but
by removing tissue from the cornea in order to change its
natural curvature.
PRK was first used to treat nearsightedness.
In a nearsighted eye, light rays come to focus in front of
the retina. By flattening the front surface of the eye, the
cornea, the eye's natural focal point can be changed so that
it focuses light more precisely on the retina. This is done
by removing tissue from the center part of the cornea.
An eye with astigmatism has an irregularly shaped
cornea. To improve the focus of an astigmatic eye, different
amounts of tissue need to be removed from different parts
of the cornea to make the surface more symmetric and eliminate
the visual distortion caused by astigmatism.
In a farsighted eye light rays come to focus
behind the retina. The cornea needs to be more sharply curved
in order to focus light rays on the retina and thus tissue
is removed from the edges of the cornea in order to make it
"steeper".
The technique of PRK involves removing the surface
"skin" of the eye in order to expose the sturdy
tissue underneath which gives the eye its shape. This is done
using a local anesthetic eyedrop and is painless. This is
different from LASIK in which a flap is cut in the cornea
to expose the tissue underneath. The laser is then used to
shape the underlying cornea in a procedure that usually takes
one minute or less. For most patients having PRK, a protective
contact lens is then placed on the eye, which allows the surface
of the eye to reheal over a period of several days, and prevents
most of the discomfort that might be associated with the recovery
period.
Usually vision improves almost immediately,
but during the recovery period vision is generally not as
good as it would be with the best possible glasses or contact
lenses. Once the protective contact lens is removed after
several days, vision continues to improve and may be at its
best level within approximately one week to one month after
the surgery. Usually eyedrops are used on a frequent basis
during the first 4-5 days to lubricate the eye, prevent infection
and decrease any inflammation resulting from the surgery.
Eyedrops are decreased rapidly over the upcoming weeks, though
in some cases patients may use eyedrops for several months
after surgery.
For additional information regarding eye care
and laser vision surgery please visit personalbestvision.com
and allaboutvision.com.
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