-1.00 to -14.50 diopters of myopia(nearsightness)
0.5 to 5.00 diopters of astigmatism
Up to +6.00 diopters of hyperopia(farsightedness)

The Excimer Laser reshapes the cornea to possibly reduce or eliminate the need for glasses or contact lenses in cases of myopia (nearsightedness) or hyperopia (farsightedness) and astigmatism. The curvature of the eye must be reshaped. There are two ways it can be accomplished with the laser, on the surface with PRK (Photo Refractive Keratectomy) or beneath the surface with LASIK.

	LASIK/Nearsightedness To treat nearsightedness, the cornea must be made flatter. This is accomplished by removing tissue from the center of the cornea
	LASIK/Farsightedness To treat farsightedness, the central cornea must be made steeper. This is accomplished by directing the laser beam to remove tissue from around this area.
	LASIK/Astigmatism To treat astigmatism, the cornea must be made more spherical. By changing the pattern of the beam, tissue is removed in one direction more than the other.

PRK

Photo Refractive Keratectomy (PRK) is a procedure that is approved by the FDA to treat mild to moderate degrees of myopia, hyperopia and/or astigmatism. It is a surface ablation technique that is an alternative to LASIK for certain individuals.