Photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK) are two similar surgical techniques that use an excimer laser to correct nearsightedness (myopia) by reshaping the cornea. The cornea is the clear outer structure of the eye that lies in front of the colored part of the eye (iris). PRK and LASIK are two forms of vision-correcting (refractive) surgery. The two techniques differ in how the surface layer of the cornea is treated. As of mid 1998, two eximer lasers (Summit and Visx) are approved for laser vision correction (refractive surgery using a laser) in the PRK procedure, but not yet approved by the Food and Drug Administration (FDA) for use in LASIK.

The purpose of both LASIK and PRK is to correct nearsightedness in persons who do not want to, or who cannot wear eye glasses or contact lenses...