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LASEK, PRK, Epi-LASIK
Procedures for thin corneas
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Over the past few years, a new method for performing the PRK procedure has emerged. This method has been termed LASEK and it seems to have some advantages for some patients. The term LASEK, is an acronym which stands for "Laser Assisted
Sub-Epithelial Keratomileusis." In this procedure we take advantage of our WaveLight Allegretto Wave excimer laser - with its amazing precision - and simply apply its vision-correcting treatment closer to the surface of the cornea. The usual LASIK flap is made up of two layers, the outermost layer is the "epithelial" layer of the cornea (about 50 microns), and the innermost layer is a portion of the sturdier corneal "stroma" (usually also about 50 microns, but this can be varied from about 40 to 100 microns). The "epithelial" layer is very soft and delicate, while the "stromal" layer is firmer and gives the LASIK flap about the consistancy of a soft contact lens.
LASEK is used mostly for people with corneas that are too thin for LASIK. This is most likely to occur when the amount of nearsighted correction is extremely large. In correcting nearsightedness the laser reshapes the cornea by removing (vaporizing) some of the "stromal" corneal tissue near the center of the cornea which is naturally its thinnest area. When the laser is finished reshaping the central cornea, the remaining central thickness must be still great enough that the cornea will be sturdy. If not, the cornea could buldge and change shape over time due to natural pressure from within the eye pushing outward. Such buldging could cause distortion of vision.
In the LASEK procedure, a confined central area of the corneal epithelium is exposed to a diluted alcohol solution (about one part alcohol and four parts sterile water) for around 30 to 60 seconds. The solution loosens the epithelium so that it can be gently separated from the underlying "stroma." The epithelium is separated, rolled up and saved with a hinge still attaching it to the cornea under the upper eyelid. The laser treatment is then applied, usually taking less than 45 seconds, and then the epithelium is rolled back into its original position over the surface of the cornea. Medicated drops are applied to the eye and a "bandage" soft contact lens is placed over the entire cornea for protection and comfort. The contact is left there for about 4 to 5 days while needed healing occurs. The patient does not have to remove or clean the contact lens, it remains in place during this time including during sleep.
After the laser treatment has been completed, the protective layer is then gently replaced over the cornea and the eye is allowed to heal naturally. Because tissue removal with LASEK is subsurface in nature, healing time is quick and the visual recovery process is improved over the PRK procedure. Most patients enjoy improved vision within 24 to 48 hours following their procedure. There may be slight discomfort for a day or so following the procedure.
WaveLight Allegretto Wave Excimer Laser |
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