The VISX excimer laser produces a specialized beam of cool ultraviolet light which removes tissue very cleanly, utilizing a process called photoablative disruption, with an eye tracker to assist in greater precision.
The laser is controlled and guided by the surgeon and specialized computer and wavefront components hosted within the excimer laser. The VISX excimer laser produces a series of rapid pulses
through a process called variable spot scanning, or flashes of intense light, that serves to remove small amounts of corneal tissue analogous to microscopic sandblasting
(photoablative disruption).
Each pulse removes and reshapes approximately 1/10,000 of an inch of tissue.
The number of pulses vary depending on the amount and type of correction being treated. The excimer laser light does not penetrate the eye and leaves surrounding eye structures (iris, lens, retina) undisturbed.
LASIK (laser assisted in-situ keratomileusis) uses the excimer laser, by applying the treatment within rather than on the surface of the cornea. A cutting instrument called a microkeratome, creates a controlled "flap" of corneal tissue which is folded back to expose the underlying corneal bed. The flap thickness varies and is approximately 130 to 180 microns. This is similar to opening a book of 100 pages to page 25 or 30.
The excimer laser pulses are applied to this internal area of the cornea.
The flap is then gently replaced back to its original position and made adherent using special fluidic techniques which are based on the concept of osmotic gradience. Because of more rapid recovery of vision with LASIK, it is possible to safely treat both eyes on the same day in most instances.
PRK or photorefractive keratectomy,
differs slightly from LASIK, in that there is no microkeratome
or flap created during the procedure. The VISX laser is
used to reshape the corneal surface in 2 steps, and a bandage
contact lens is placed onto the eye to aide in comfort and
visual restoration. Usually the contact lens is left
in place until the corneal tissue beneath it is restored,
which takes 3 to 5 days, variably from eye to eye. Special
medicated eye drops are used following PRK procedures, that
are imperative they be used exactly as the surgeon prescribes
as otherwise the end result of the procedure is adversely
affected. PRK procedures intraoperatively are very comfortable
and easy from the patient and surgeon perspective since
no flap is being created. However, the postoperative period
warrants more frequent visits to the surgeon initially,
with a longer period of eye drop usage. PRK is most commonly
used today to treat refractive errors in eyes that are too
flat, too steep, too thin, or that have recurrent corneal
erosion/map dot corneal dystrophy contained within them
(LASIK is less ideally suited for eyes with recurrent corneal
erosion or map dot corneal dystrophy).
Learn more about
LASIK Benefits, click here.
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