The cornea and lens combine to focus visual images on the back of the eye. When the overall length of the eye is incorrect or when the curvature of the cornea is incorrect, the visual images are not in focus. The cornea accounts for approximately 2/3rds of the focusing power of the eye. By surgically changing the corneal curvature, visual images can be brought into focus.

Laser In Situ Keratomileusis (LASIK) and Photo-Refractive Keratectomy (PRK) are two surgical techniques which utilize the excimer laser to reshape or change the curvature of the cornea.

LASIK utilizes conventional and laser surgery to correct nearsightedness, farsightedness and astigmatism. LASIK can correct nearsightedness and farsightedness with or without astigmatism, with excellent results (95% of patients achieve 20/40 vision or better).

In performing LASIK, eye drop anesthetic is used to numb the eye. The surgeon then uses a special instrument to create a corneal flap. The flap is retracted and the eye is positioned under the excimer laser (which has been computer programmed to remove microscopic amounts of the internal corneal tissue). Removal of the tissue changes the curvature of the cornea. If the patient is nearsighted, tissue closer to the central part of the cornea is removed to decrease the curvature or flatten the cornea. If a patient is farsighted, tissue in the peripheral part of the cornea is removed to increase the curvature of the cornea. To correct for astigmatism, tissue is removed along the axis of the astigmatism. After the laser has been used, the flap is returned to its original position. The corneal tissue has extraordinary natural bonding qualities that allow effective healing without the use of stitches.

Since only local anesthetic is used, patients remain awake during the procedure. The entire procedure takes only a few minutes. Improved vision is often possible on the day following the surgery. Eye drops and night protection are necessary for designated periods of time.


Photo-Refractive Keratectomy, PRK is another method of surgically reshaping the cornea using the excimer laser. The difference between LASIK and PRK is that for PRK, the corneal flap is not created. That is, the outer layer of the cornea remains in place and the laser removes tissue directly from this outer layer. PRK can be used for low to moderate amounts of nearsightedness. The healing period for PRK is longer and usually only one eye is treated at a time.


The LASIK Procedure


nearsighted eye


farsighted eye






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