LASIK
LASIK, an acronym for Laser-Assisted In Situ Keratomileusis is a form of refractive laser eye surgery procedure performed by ophthalmologists (MD/DO) intended for correcting the vision in order to reduce a person's dependency on corrective devices, such as glasses or contact lenses. The procedure is usually a preferred alternative to PRK, or photorefractive keratectomy, as it requires less time for full recovery, and the patient experiences less pain overall.
History
LASIK surgery was developed in 1990 by Dr. Lucio Buratto (Italy) and Dr. Ionnis
Pallikaris (Greece) as a melding of two prior techniques, keratomileusis and
photorefractive keratectomy. It quickly became popular due to its improved
precision and lower frequency of complications compared to those techniques.
In 1991, LASIK was performed for the first time both in Europe and in the United
States (by Dr. Stephen Slade)
Surgical procedure
Pre-operational Corneal mapping
Several days before the procedure, the surface of the patient's corneas are
examined with a computer-controlled scanning device to determine their exact
shape. Using low-power lasers, it creates a topographic map of the cornea. This
process also detects astigmatisms and other irregularities in the shape of the
cornea. Using this information, the surgeon calculates the amount and locations
of corneal tissue to be removed during the operation.
Also, the patient is typically prescribed an antibiotic to start taking beforehand, to minimize the risk of infection after the procedure.
The Operation
The operation is performed with the patient awake and functional, however, the patient is typically given a mild sedative (such as valium) and anesthetic eye drops. The surgeon operates the lasers, which make all of the incisions. A computer system tracks the patient's eye position 4,000 times per second, redirecting laser pulses for precise placement. A flap is cut in the cornea using a blade (called a microkeratome) or a femtosecond laser. A hinge is left at one end of this flap. The flap is folded back revealing the stroma, the middle section of the cornea.
Then an excimer laser (193 nm) is used to remodel the corneal stroma. The laser vaporizes tissue without causing damage to adjacent stroma in a finely controlled manner. The layers of tissue removed are tens of micrometres wide.
Post-operational complications
While in nearly all cases the operation is a success, the procedure does have some rare complications. A slipped flap (when the corneal flap detaches from the rest of the cornea) is one of the most common complications. The chances of this are greatest immediately following surgery, so patients are typically recommended to go home and sleep, to let the flap heal.
Infection under the corneal flap is possible. It is also possible that the patient has a genetic condition that causes the cornea to thin out following surgery. While this is screened for in the pre-op exam, it is possible in rare cases (about 1 in 5,000) for the condition to remain dormant until later in life (the mid-40s). If this occurs, the patient will require a corneal transplant.
Factors affecting the surgery
The cornea contains fewer blood vessels than most tissue, as it must be transparent to function normally. The corneal cells absorb oxygen from the air and tears. However, long term use of contact lenses reduces this absorption of oxygen, resulting in increased development of blood vessels. This can cause a mild increase in inflammation and healing time, and some psychological discomfort during the surgery due to augmented bleeding. These consequences may inspire contact lens users to be more responsible about neglecting to remove lenses before sleeping.
LASIK technology
The technology is improving at a rapid pace, but a large body of conclusive evidence on the chances of long-term complications is not yet in place. Also, there is a small chance of complications, such as slipped flap, corneal infection, haziness, halo or glare, amongst others. The procedure is irreversible.
A 2004 Wake Forest University study found that Lasik results are affected by heat and humidity, both during the procedure and in the two weeks preceding surgery[4].
The NHS National Institute for Clinical Excellence's December 2004 guidance on laser eye surgery [5] found that evidence is weak for its effectiveness in treating severe short- or long-sightedness (only 26-36% had an uncorrected visual acuity of 20/20 or so); that 5% of cases had complications; and notes concerns about long-term safety of thinning the cornea.
The source of this article is Wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL
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