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Photoablative Refractive Keratectomy (PRK),
Laser Epithelial Keratomileusis (LASEK), or Epi-LASIK
PRK surgeries have been performed since 1989. This procedure is proven
effective to correct nearsightedness up to -6 diopter and astigmatism
up to approximately 3 diopter.
The PRK procedure
During PRK laser eye surgery, a surgeon uses the computer-controlled cold
light excimer laser to reshape
the cornea. This laser delivers a cool pulsing beam of ultraviolet light
to the surface of the cornea, not underneath the cornea, like in LASIK.
Therefore, no incision is required. The laser removes tiny particles of
the cornea (ablation) to change the refractive power at the surface of
the corneal center. The outer surface of the cornea regenerates itself
within approximately 3 to 4 days. For the first two days after surgery,
patients may experience eye pain or irritation. These side effects can
be reduced by wearing a therapeutic contact lens or taking adequate medication.
Medicated eye drops are also prescribed for the first few weeks after
surgery.
The LASEK procedure
LASEK is a relatively new variation of PRK used mostly for people with
corneas that are too thin or too flat for LASIK. In LASEK, the epithelium
(the outer layer of the cornea) is cut not with the microkeratome cutting
tool used in LASIK, but with a finer blade called a trephine. Then the
surgeon covers the eye with an alcohol solution for around 30 seconds.
The solution loosens the edges of the epithelium. After sponging the alcohol
solution from the eye, the surgeon uses a tiny hoe to lift the edge of
the epithelial flap and gently fold it back out of the way. Then an excimer
laser, as in LASIK or PRK, is used to sculpt the corneal tissue underneath.
Afterward, the epithelial flap is placed back on the eye with a kind of
spatula.
The Epi-LASIK procedure
With Epi-LASIK, a special microkeratome is used to lift the epithelium
like a flap. This flap can be repositioned after the ablation is finished.
Treatment of corneal problems
PRK is also used as a special therapeutic treatment to remove surface
scars or chronic lesions on the cornea. In this case, it is referred to
as PTK (Phototherapeutic Keratotomy).
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