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LASEK
LASEK stands for laser-assisted subepithelial
keratectomy. It is sometimes called epi-lasik.
It is similar to LASIK except in one important way–no
corneal flap is necessary. With LASIK, a corneal flap
is created, beneath which the laser removes corneal
tissue to correct a prescription. With LASEK, no thick
corneal flap is required; the laser removes tissue directly
from the surface of the cornea, after the very superficial
layer or covering called the epithelium, is temporarily
removed. The laser treatment itelf is identical.
Surgical Procedure
Remember that the cornea has many layers. The very surface
layer is called the epithelium. This layer behaves very
much like the superficial layer of the skin, the epidermis.
The epidermis is contantly being shed and replaced with
new epidermis. The corneal epithelium likewise is constantly
growing and being replaced. The corneal tissue beneath
the epithelium is much more firm and thick; it is called
the stroma.
In the lasek procedure, the epithelial or surface layer
is loosened with a softening agent made of dilute, medical-grade
alcohol. The sheet of loosened epithelium is then carefully
pushed aside, much like you would push a throw rug aside
to vacuum the carpeting underneath. The exposed corneal
stroma is now ready to be lasered.
After the laser correction has been performed, the
sheet of epithelium is pushed back into place, to cover
the remaining corneal stroma. Usually, a soft contact
lens is placed onto the cornea for protection and comfort.
Standard antibiotic and non-steroidal anti-inflammatory
drops are placed into the eye at the conclusion of the
procedure.
Epi-LASIK is very similar to LASEK,
in that the surface layer, the epithelium, is separated
from the underlying corneal stroma, but it is done using
a mechanical device rather than an alcohol treatment.
The Amadeus microkeratome, from Advanced Medical Optics,
creates epithelial flaps of unsurpassed quality.
LASEK vs. LASIK
There are some patients who are not candidates for lasik
because they have corneas that are too thin (see Corneal
thickness and Pupil
size). The stronger a prescription, the more corneal
tissue that has to be removed with the laser (the deeper
you have to go). There is a limit to how much tissue
can be safely removed with laser vision correction.
To use an analogy, I can make the walls of a house thinner,
but if too thin, they may not hold up the roof. If a
person does not have corneas thick enough to safely
correct his or her prescription, lasek may be an alternative.
Since no corneal flap is needed, the laser removes corneal
tissue more towards the surface, leaving more untouched
tissue below. The more untouched tissue left behind,
the stronger the cornea as a whole.
Other patients may not be candidates for lasik because
their corneas exhibit an irregularity which makes lasik
unsafe. These corneal dystrophies, as they are known,
make the superficial epithelial layer very loose under
normal circumstances. With lasik, it is important that
the epithelium be left intact at the conclusion of the
procedure. Patients with certain corneal dystrophies
are ideal candidates for lasek.
Patients who have dry eye may fare better with lasek
than lasik. Lasik can be associated with dry eyes; usually,
this is a temporary situation. It is felt that the creation
of a lasik flap can contribute to dry eyes by compromising
corneal nerves. Since no flap is made with lasek, such
compromise is less likely.
Some patients prefer to have lasek rather than lasik,
simply because they don’t want a flap.
Recovery and comfort with LASEK compared to
LASIK
Visual recovery with lasek is slower. It is hard to
predict how quickly vision will improve, but improvement
begins immediately. Most patients are able to pass the
driver’s vision test within a few days of the
procedure. Most can return to work within a week.
The lasek procedure is not painful. There is no pain
during the actual procedure. Patients may have irritation
after the surgery, during the healing period. Even though
the epithelium layer is intact, it needs to remodel
(like rearranging your clothes to make them fit better).
With appropriate use of drops, and pain medications,
if necessary, lasek patients can have an uneventful
recovery period.
Visual results with LASEK
The visual results are just as good as those with lasik.
There is no compromise with the vision.
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