This highly successful procedure combines the best qualities of two previously approved refractive surgical techniques: Automated Lamellar Keratoplasty (ALK) and Photorefractive Keratectomy (PRK). Although these two procedures have been virtually supplanted by the LASIK (Laser In-Situ Keratomileusis) procedure, we believe you will better understand LASIK if you know something about the procedures from which it was derived.
Photorefractive Keratectomy (PRK): The excimer lasers employed in all laser-based refractive surgery were first approved by the FDA for the PRK procedure in late 1995 after nearly ten years of extensive testing. As with all corneal refractive surgery aimed at correcting nearsightedness, the objective of PRK is flattening of the central cornea in order to focus light properly on the retina.
The first step in PRK is removal of the corneal epithelium, the thin, outermost layer of the cornea. This is usually achieved with the help of surgical instruments. The excimer laser, a computer-controlled device capable of very precisely removing thin layers of tissue, then ablates (vaporizes) corneal tissue in order to “sculpt” the corneal surface into the desired shape. The pattern of sculpting is determined by measurements from your preoperative evaluations, which are input into the laser’s computer. Under the skillful guidance of your surgeon, the computer directs the firing of the laser to achieve the specified pattern. Healing is delayed, with discomfort common during the first few postoperative days.
Automated Lamellar Keratoplasty (ALK): The basic procedure of ALK was developed by a Columbian physician in 1949, but was not widely accepted until refined over many years. It is capable of correcting very large degrees of myopia. The ALK procedure employs an instrument called a microkeratome to create corneal flaps, allowing the necessary reshaping of the cornea. Healing time is very rapid, usually within 24 hours, with rapid restoration of vision and little discomfort. The procedure is less accurate than laser-based surgery.
Laser In-Situ Keratomileusis (LASIK): This highly successful procedure combines the minimal postoperative discomfort and rapid visual recovery of ALK with the computer-controlled precision of PRK. LASIK is now the most commonly performed refractive surgical procedure in the world.
As with ALK, the initial step in LASIK is creation of a corneal flap using either a microkeratome, or more commonly the IntraLase laser (see details below). Once the flap is folded out of the way, the excimer laser is used to sculpt the cornea as determined by ocular measurements. The corneal flap is then gently repositioned by the surgeon, sealing down within minutes. Vision is often good within 24 hours with minimal discomfort. Complete healing takes about one month
For more information about the LASIK procedure, read the following step-by-step explanation of the surgery.