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PRK or Photorefractive Keratectomy was actually the first Excimer laser procedure approved for the correction of nearsightedness in the mid 1990’s. It is presently used for the correction of nearsightedness (myopia), farsightedness (hyperopia), and astigmatism.
Like LASIK, PRK uses the laser to gently reshape the surface of the eye providing clearer vision. Unlike LASIK, PRK does not involve the creation of a surface flap. With LASIK, an instrument called a microkeratome is first used to create a thin flap in the cornea (the front windshield of the eye). This flap is then retracted out of the operative field and laser is applied to the underlying corneal tissue. The flap is subsequently replaced into its original position. PRK, however, has no flap. The laser is instead applied directly onto the surface of the eye to perform the visual correction. Since there is no flap to replace over the treated surface, a contact lens is placed on the eye to promote healing and to provide comfort. This lens requires no maintenance and is usually removed after several days by your doctor. PRK typically provides excellent results for patients with low to moderate myopia, astigmatism and hyperopia.
PRK has advantages over LASIK. For example, while rare, the possibility of a flap complication with LASIK procedures does exist. However, since there is no flap with PRK, there is no risk of this problem. PRK is also an option for many patients who cannot have LASIK due to significant dry eye problems or if the cornea is too thin for LASIK.
PRK had somewhat fallen out of favor with the advent of LASIK in the late 1990’s. Additionally, in the early days of PRK, patients experienced significant discomfort due to the treatment leaving a large abrasion on the surface of the eye. PRK has, however, recently become more popular due to its relative low risk. Additionally, new surgical techniques such as LASEK (pronounced “Lay –SEEK”), a form of PRK, and chilled stromal irrigation have greatly improved the comfort level post operatively.
Today, the main disadvantage of PRK is longer recovery time. The surface usually takes 3-6 days to heal sufficiently for the contact lens to be removed. Visual recovery then takes an additional period of time from days to weeks. Once the eye has achieved good vision, the second eye can then be done if desired. This is in contrast to LASIK where both eyes are typically done on the same day and visual recovery is measured in hours or a few days. One other disadvantage of PRK is the need to use eyedrops for a longer period of time, sometimes several months versus a few days for LASIK.