LASIK is a shortened term standing for "LAser in SItu Keratomileusis". This correction procedure utilizes two devices to alter the degree of near-sightedness, astigmatism, and far-sightedness in an eye. These two devices are the excimer laser and the corneal flapmaker (either the microkeratome or Intralase laser).

After anesthetic eyedrops are put on the eye, a suction ring is centered over the cornea of the eye. This suction ring stabilizes the position of your eye and increases the pressure to a level that is needed for proper functioning of the microkeratome or the Intralase flapmaker.

After the flap has been made, the suction ring is removed, and the corneal flap is folded back on the hinge, exposing the remaining corneal tissue.

NEARSIGHTEDNESS CORRECTION

If nearsightedness is being corrected, the excimer laser is then used to remove tissue and reshape the center of the cornea. The amount of tissue removed is dependent upon the degree of near-sightedness that is being corrected.

In the final step, the hinged flap is folded back and it self seals in its original position. The front surface of the eye is now flatter since the flap conforms to the underlying surface. In effect, the change made in the middle of the cornea is translated to the front surface of the cornea.

ASTIGMATISM CORRECTION

The excimer laser can be used to treat astigmatism while performing LASIK. Astigmatism measurements describe to what degree the cornea is "non-spherical." As an example, the surface of a basketball is spherical and would have no astigmatism. The surface of a football, on the other hand, would be highly non-spherical and would have high astigmatism. The excimer laser reduces the degree of astigmatism by removing corneal tissue in an asymetric manner, utilizing an oval-shaped beam.

FARSIGHTEDNESS CORRECTION

If farsightedness (hyperopia) is being corrected, the cornea is flatter than is required given the length of the eye. Hyperopic LASIK is used to reshape the front surface of the eye, making it more curved.

In hyperopic (farsighted) treatment, a "donut" of tissue is removed from the mid-periphery of the cornea as shown in the picture above. This changes the profile of the cornea to steepen the central curvature.