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Types of laser surgeryThere are three main techniques currently being used today. 10 years ago, RK was the most common. PRK started to be employed about this time, and finished it's 7 year FDA trial period in the United States in October 1996. LASIK is the newest technique, and is about 5 years old at this point. It was not really in use on patients until about 2 years ago. Interestingly, Canadian eye surgeons were not bound by the same regulations, which forbade any change in protocol or procedure during the 7 year trial, and so were free to experiment with changing various aspects of the procedure based on patient results. This put Canada at the forefront of refractive surgery, and still today Canadian doctors are at the leading edge in this field.Radial Keratotomy
In this technique, radial incisions are made to 9/10ths the thickness of the cornea around the peripheral part, leaving the central 4-5 mm untouched. The higher the myopia, the more incisions are required. These incisions weaken the cornea structure, and the intra-ocular pressure of the eye makes the weakened periphery bow out, causing flattening of the corneal curvature centrally. This flattening in the optic zone is what reduces the nearsightedness.
While RK is the least expensive refractive surgery technique, it has several draw-backs. The scars from the incisions are permanent, and will intrude into the optic zone, especiallty in dark situations, causing night glare. Some RK patients even take pupil constricting drugs to avoid this. The weakened corneal structure does not bode well if eye trauma occurs later on. RK is much more dependent upon physician skill, and in the hands of an experienced surgeon, can produce good results, but is definitely on the decline as computer controlled laser surgery becomes the method of choice. PRK
Photo Refractive Keratectomy is the most common type of refractive laser surgery done today, and is probably the most tried and true technique. The excimer laser is used to directly reshape or flatten the central cornea, leaving the peripheral part alone. The laser will typically remove only about 1/10th the thickness of the central cornea, and is a much less invasive technique than RK. The structural integrity of the cornea remains intact.In order to reshape the cornea, the outer cover or epithelium must be removed. This does take several days to grow back entirely, and during this time you will experience really terrible vision and a fair bit of discomfort. Typically Demerol is used to control the pain during the 3-4 days post-op. The cornea does undergo some swelling after PRK as well, and this produces haze. This dissipates gradually, and you are pretty much normal about a month after the procedure. You can expect to take AT LEAST 1 week off work to recover from PRK. LASIK
Laser in situ Keratomileusis is the latest development in refractive surgery, and will likely replace PRK in the next several years as the technique of choice. In LASIK, a microkeratome (like a carpenter's plane) is used to partially slice open the top third of the cornea, and the surgeon then opens this section of tissue and folds it back like a flap. This allows most of the surface epithelium to remain undisturbed, which leads to a lot faster recovery times. Then, just as in PRK, the laser is used to re-shape the cornea internally, the flap is put back in place, and the patient sent home. Good vision can be regained in as little as a couple of days, as only the thin hemi-spherical incision around the flap must heal. There is less haze because there is less corneal disturbance. LASIK is still under-going modification and improvement, and is only offered by a few leading edge surgeons for now. It was originally developed in part by Dr. Jeff Machat of TLC, who is a world authority on LASIK currently. LASIK cannot be performed on patients with minimal starting corneal curvature (flat eyes). There are more potential complications possible with flap dis-lodgement even up to 6 months post-op. It is probably more exact in correcting high myopes than PRK, and will likely continue to improve and supersede all other forms of refractive surgery in the coming years.
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