Laser In-Situ Keratomileusis (LASIK)

What is LASIK?
How is the procedure performed?
What are the advantages of LASIK?

What is LASIK?

LASIK is now the most popular of all laser vision correction procedures. It is estimated that 1½ to 2 million procedures will be completed in the United States in the year 2000. This highly successful procedure combines the minimal postoperative discomfort and rapid visual recovery of the Automated Lamellar Keratoplasty (ALK) procedure with the computer-controlled precision of the Photorefractive Keratectomy (PRK) procedure.

The first step in the LASIK procedure is the creation of a flap of tissue from the outer layer of the central zone of the cornea using the microkeratome. The flap is then folded back out of the way, but it is held ready for replacement upon completion of the procedure. The excimer laser is then used to sculpt the remaining central zone in accordance with pre-determined data that has been entered into the laser system’s computer. Under this precise control, the laser reshapes the curvature of the cornea to correct for nearsightedness, farsightedness or astigmatism. This part of the procedure takes only 30 to 60 seconds, after which the corneal flap is replaced. No sutures are used, and the surface of the eye will normally heal itself. Most patients can see quite well within 24 hours or less. Complete healing of the cornea takes about one month.

The LASIK procedure is performed on an outpatient basis. Although the actual laser procedure takes only a few seconds per eye, the procedure requires a couple of hours at the surgery center. Some of this time is spent preparing the patient for the procedure, while a few minutes are required afterwards for post-operative instructions and departure preparation.

How is the procedure performed?

Step 1: Eye preparation
Before the procedure begins, a nurse or technician talks to the patient about any immediate health problems that may affect readiness for the procedure. Antibiotic and anesthetic eye drops are then placed in the eye to numb it and prevent infection. The eye is swabbed with a sterile solution. The eyelid is then propped open with a lid retainer, and a paper or plastic "mask" is placed over the eye to keep eyelashes out of the way. Then the cornea is marked with a blue "dye ring," which serves as a reference point for the surgeon throughout the procedure. Because the cornea is numb, most patients experience little if any discomfort during these pre-operative preparations.

Step 2: Creating the flap
Next, the doctor creates a flap from the central zone of the cornea using the microkeratome. This precision instrument works much like a miniature carpenter’s plane. It contains a disposable cutting blade that is preset according to the thickness of the cornea — usually about 160 to 180 microns or 1/3 the depth of the cornea. The microkeratome operates in conjunction with a suction ring that holds the eye perfectly still, and when activated by a vacuum tube, it raises and flattens the cornea so it can be reached easily for cutting the flap.

Step 3: The Excimer laser
After the flap has been folded back from the center of the eye, the doctor dries the underlying cornea with a sponge-tipped swab and aligns the Excimer laser’s microscope with the central corneal area in order to monitor the laser’s sculpting pulsations. The patient is asked to focus on a fuzzy red light inside the laser. As the doctor activates the laser, there is a "popping" or "tacking" sound, and there is a slight odor similar to that of hair burning, but no discomfort for the patient. The number of laser pulsations will depend on the nature of the refractive vision problem that is being corrected. This phase of the procedure takes only a minute or so. The doctor then carefully folds the flap back in place and irrigates the eye with a sterile saline solution. The corneal area may be dried with a gentle blower, which helps seal the flap. In addition, a contact lens may be placed in the eye.

Step 4: Post-operative measures
When the procedure is complete, additional antibiotic drops are placed in the eye, and it may be covered with a plastic shield. For a short while after the procedure, the eye is numb from the anesthetic drops. As the numbness wears off, the patient may experience some light sensitivity and a scratchy or dry sensation as though something is in the eye. This feeling usually goes away within a few hours. Patients must not drive themselves home following the procedure.

The patient returns to the doctor’s office the next day for a post-operative examination. The doctor checks the flap to see if it is healing properly. If a contact lens was placed after surgery, it will be removed at this time. Vision is checked and, for most patients will range from 20/20 to 20/40 depending on the number of laser pulsations received. For some patients, vision may continue to improve for several weeks before totally stabilizing.

What are the advantages of LASIK?

The LASIK procedure has several advantages over both the ALK and the PRK procedures on which it is based. Although it employs the Excimer laser precision control and accuracy of the PRK procedure, the LASIK procedure does not remove any part of the epithelium, the thin, film-like protective outer layer of the cornea, as does PRK, and there is less chance of scarring. Thus, the primary healing process is the resealing of the corneal flap, which usually happens within 24 hours and with little post-operative discomfort. The LASIK procedure can also handle successfully higher degrees of myopia than PRK and can be used to treat cases of farsightedness and astigmatism.