LASIK is an acronym which stands for laser in situ keratomileusis, a surgery which corrects nearsightedness. The operation uses two devices, an ultraviolet laser and a microkeratome, a surgical instrument with an oscillating blade. This precision shaver is used to cut a thin slice from the cornea, the transparent outer layer of the eye which covers the iris and the pupil.
During the LASIK procedure, a suction ring is put around the cornea to hold it into place and to establish the correct pressure needed for the operation. The microkeratome then moves along the tracks on the side of the ring, cutting a flap in the cornea. Once the cornea has been opened, the laser is used to reshape the cornea by removing tissue in order to correct the vision. After the appropriate amount of tissue has been removed, the flap is placed back down, where it conforms to the new shape of the cornea.
The microkeratome was first developed in the 1950s in Latin America by Jose Barraquer, and was designed after a carpenter’s plane. The device was used to surgically correct visual impairment, but the results were unpredictable, and the first surgical methods using this instrument failed to gain popularity. The development of lasers to use in conjunction with the microkeratome is much more accurate, and has become the most popular method of repairing nearsightedness.
There are two types of microkeratomes; mechanical and laser. The mechanical version has an oscillating blade which can move 12,000 revolutions per minute (RPM). The blade is attached to a rotating shaft, which is in turn connected to a gas or electric turbine. The blade can be moved either manually or mechanically. It is extremely important that the pressure be kept on the eye by the ring during this procedure, and that only sharp blades are used to help eliminate any negative side effects.
The laser version uses light energy to create bubbles under the cornea at a preset depth. Thousands of these bubbles form to create the incision. One of the benefits of the laser unit is that there are no blades to replace, and the accuracy of the cut does not depend on the surgeon’s steady hand. Both mechanical and laser products are precise, but the laser unit appears to produce more consistent results and thinner cuts. A single-use microkeratome with disposable components has been developed which produces a thinner flap, similar to those made by the laser version.
In some instances, post-operative complications can arise, and a few of them are connected to the flap. Fortunately all such complications are treatable and can be corrected in a short period of time. Some eye surgeons have migrated away from using the mechanical microkeratome in favor of using two lasers, hoping to eliminate complications with the flap and to achieve a thinner, more consistent cut. The traditional microkeratome is still a popular choice with many eye surgeons, however, because of its long track record of success and lower cost.
