Howerton Eye Clinic - Austin Texas
LASER IN SITU KERATOMILEUSIS (LASIK)
by Shawn Powell - Austin, Texas

LASIK, laser vision correction, is a procedure for the correction of moderate to high degrees of myopia (nearsightedness). LASIK will also correct low to moderate degrees of hyperopia (farsightedness) and astigmatism associated with myopia.

In order to really understand the LASIK procedure, the patient must have a working knowledge of the Cornea. The Cornea is a clear window to the eye and is transparent tissue. Generally, the cornea is 11.5mm in horizontal diameter, which is roughly ½ inch. The center most portion of the cornea is about 500 microns thick.

The day of the procedure begins with the arrival at the center of choice. Of course, the first matter at hand is collection of payment and consent forms. Oral Valium, in most cases, is dispensed to relax the patient. Pre-operative topical antibiotic, anti-inflammatory and anesthetic drops are given.

The patient will be escorted into the surgery suite. The surgeon will then examine the eye under the slit lamp and will apply a gentian violet dye to the pupil. These markings give orientation for astigmatism, when patients lie down their eyes tend to roll slightly; therefore, these marks allow for a perfect line up. Also in the case of a “free flap”, the mark would allow proper orientation of the cap back on the eye.

The patient is now ready to be placed in position in a reclining surgical chair. Eyelashes are covered with a plastic drape and a speculum, lid holder, is inserted to hold your eyelids open. The opposing eye is patched closed. LASIK is most commonly performed bilaterally (both eyes on the same day). Patients remain awake during the procedure, and the eye is numbed with drops. There is no discomfort during the procedure.

The patient will be asked to focus on a light, most surgeons provide a coach or hand holder to assist the patient through the process. The coach’s job is to tell the patient everything that is going to happen before it happens. Patients will also be reminded to focus on the light, keep still, and breathe normally.

The surgeon will begin the placement of the suction ring (the microkeratome blade will attach to this), once good positioning is obtained, suction is applied. The patient will generally feel pressure and vision will go dark; however, there is no pain involved. The microkeratome will be placed on its track, after an adequate amount of pressure is fulfilled. The surgeon will then start the microkeratome blade across the cornea creating the flap. The flap is left attached to the cornea by a hinge, which is made by having the microkeratome stop before it fully traverses the diameter of the cornea, leaving an uncut portion. The flap is 160-180 (about 4 human hairs) of the 500 microns. The patient will hear a buzzing sound and feel a mild vibration. Once the flap is complete, the suction ring and the microkeratome are removed.

The flap is then lifted by the surgeon, and folded back out of the way. Then the excimer laser is used to reshape the remaining surface of the cornea. The laser treatment typically lasts less than one minute. During the laser treatment, the patient will hear the click sound of the laser and might also smell a slight burning odor. The treatment will last from 30 to 90 seconds. One diopter of correction will take approximately 8 seconds. The surgeon has control of the treatment at all times. Should the eye move off center, the surgeon could stop and then restart the laser treatment. The amount of laser treatment necessary is based on the patient’s particular prescription. This information was programmed into the laser prior to arrival for surgery.

Once the laser treatment is complete, the surgeon will irrigate the treated area and lay the flap back into its original place where it will adhere to the eye without the need for sutures. Topical drops will be applied and the area will be smoothed. Most surgeons wait 1 to 3 minutes to insure the corneal flap has fully re-adhered. At this point, patients can blink normally and the corneal flap remains secured in position by the natural suction within the cornea. While it is possible to dislodge the corneal flap during the first day or two by physically rubbing the eye, this event is actually quite rare. Before the patient leaves, the surgeon will examine both eyes to insure that the flap is still in position.

Since the protective layer remains intact with LASIK, patients are only placed on an antibiotic and anti-inflammatory drop for about a week. Preservative Free artificial tears are used initially for dryness. Vision is usually quite good the following day with LASIK.
LASIK patients are instructed to wear protective eye shields while sleeping the first night to prevent accidental trauma to the cornea flap during the early healing period. The excimer laser is an ultraviolet laser, which utilizes Argon and Fluorine gas to create a non-thermal, or cool beam, of laser light, which can break molecular bonds in a process commonly, referred to as "photoablation". A simple way to imagine how the laser works is to think of it as placing the curvature from your glasses or contact lenses onto the front surface of your eye, allowing you to see without corrective eyewear.

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