uses the excimer laser to correct low to moderate amounts of refractive errors. PRK treats nearsightedness by removing corneal tissue from the surface of the cornea, causing the central optical zone to flatten. This allows light rays to focus more directly on the retina, thereby reducing nearsightedness. The amount of tissue to be removed is determined by the amount of nearsightedness to be corrected. For most patients, only five to ten percent of the cornea is removed to obtain the desired results.
Photo-Astigmatic Refractive KERATECTOMY (PARK) can be used to treat low to moderate amounts of astigmatism. Since regular astigmatism is caused by the cornea being steeper in one direction, like a football, the excimer laser beam is shaped to remove more tissue in one direction than the other. The result is a more spherical cornea that allows light to focus more directly on the retina. PARK can usually be done in the same session as PRK or LASIK.
LASIK is an acronym for LASer In-situ Keratomileusis, which simply means "to shape the corena within using a laser." It corrects vision by reshaping the cornea (outer window of the eye) so that light rays focus more precisely on the retina, thereby reducing or eliminating refractive errors.
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