Performed since the early 1970's, refractive surgery procedures improve vision for people with nearsightedness (myopia), farsightedness (hyperopia), and astigmatism. Laser assisted In-Situ Keratomileusis (LASIK) is an excellent technique for reshaping the surface of the cornea to correct these common vision problems.
Lasik is an acronym for the procedure known as Laser Assisted In-Situ Keratomileusis. It is a two step procedure which essentially combines the long ago described technique called ALK (automated lamellar kertomileusis) with PRK. In ALK a special instrument was used to create a thin cap of corneal tissue. This cap was laid aside and then a second cut was made to the remaining cornea. This second cut was the one that allowed someone's refractive error (for example their near-sightedness) to be reduced. The cap was then repositioned and the eye allowed to heal. The problem with this procedure was that it was very difficult to make the second cut in a reproducible way on different patients. Therefore, it was difficult to predict what the results of the procedure would be on any given patient. In PRK, the excimer laser is used to reshape the corneal surface in what has proven to be a predictable fashion. Several years ago the idea arose to use the excimer laser to perform the second part of the ALK procedure. Instead, it is left attached by a hinge of normal corneal tissue and folded safely back out of the way. The laser is then applied to the remaining cornea. The cap is then repositioned and allowed to seal itself in place. In the typical procedure this does not require the use of stitches. By not completely removing the cap it is much easier to return it to its appropriate orientation on the cornea.
LASIK has allowed many individuals function with a greatly reduced dependency on glasses and contact lenses. However, this procedure is not necessarily for everyone. The key as to how well one might be predicted to do with this procedure depends on several factors including their refractive error (eyeglass prescription), the health of their eyes and their expectations. Most individuals (95%) that are considered to be good candidates will achieve an uncorrected vision (vision without glasses or contacts) of 20/40 or better. As you may well know, many of these patients were functionally blind at a distance when they didn't wear corrective lenses prior to having LASIK.
An important point to understand is that while LASIK has the ability to correct several types of refractive errors, it cannot correct presbyopia. Presbyopia is the phenomenon that occurs to every person some where around the age of 40. This is where the eye loses it ability to increase its focusing power to allow one to read up close. This is a normal aging process and happens to all of us regardless of whether we are nearsighted, farsighted or never needed glasses for distance our entire lives. This is why one has to resort to reading glasses or bifocals. There is no reliable procedure available to correct this.
LASIK is being used to help people who are nearsighted (myopic), farsighted (hyperopia) and with astigmatism when combined with one of these others in an appropriate amount. Of great importance is that one's prescription has been stable for one year. The patient must be at least 18 years old for myopia and 21 for hyperopia and astigmatism. There truly is no upper age limit, although if someone is close to needing cataract surgery we advise against having any refractive procedure as quite often the problem can be addressed through the cataract operation.
For myopia the general range that can be treated is -1.00 to -10.00 or perhaps -12.00. The upper range will depend on the individuals corneal anatomy and their expectations both of which are determined as part of the pre-operative evaluation. Their can be up to 4.00 diopters of associated astigmatism.
For hyperopia the range is +1.50 to +6.00 with less than or equal to 1.00 diopter of astigmatism.
There are a few eye diseases, as well as systemic (general) disease that would make one a poor candidate for refractive surgery of almost any kind. These are best discussed with your eye doctor.
While LASIK is very effective and most patients do well, it is important to remember that it is a real surgical procedure. Like any surgery there are always some risks to consider. Any person considering refractive surgery should carefully weigh for themselves the risks versus the increased freedom and quality of life they stand to gain from a decreased dependence on corrective eyewear.