Refractive Surgery
Until recently, refractive errors could only be corrected with glasses or contact lenses. Today, patients have several surgical treatments available in addition to corrective lenses to treat refractive errors such as astigmatism, and hyperopia. Not all people with refractive errors are good candidates for refractive surgery. Your optometrist is the best source of information on refractive procedures and your options based on your particular refractive errors.
Below is information on the most frequently performed refractive surgeries:
Radial Keratotomy
RK is a surgical procedure to correct myopia in which a calculated number of incisions are made in the periphery of the cornea to allow the central cornea to flatten. The incisions are made in a spoke-like fashion radiating from the cornea. Flattening the cornea reduces the cornea's optical power and allows light and images to focus on the retina. The procedure is usually performed in the ophthalmologist's office under a local anesthetic. RK is most effective on patients with low to moderate myopia who require up to 5 diopters of correction.
Astigmatic Keratotomy
AK treats astigmatism, as the name suggests. AK is similar to RK in that it is incisional surgery, but the calculated surgical incisions are made traverse to the cornea. AK may be performed in conjunction to RK.
Automated Lamellar keratoplasty
ALK is most effective on patients with moderate to significant degrees of myopia or hyperopia. In ALK for myopia, the ophthalmologist places an instrument called an automated microkeratome on the eye which removes, in a shaving motion, a thin layer of cornea only microns thick. An even thinner layer of cornea underneath this top cap is removed, and the top cap is replaced. The procedure does not require sutures.
Photorefractive Keratectomy
PRK is a relatively new surgical procedure for the treatment of mild to moderate myopia. The procedure is often referred to as Excimer Laser Surgery, after the surgical laser used to perform the procedure. In PRK surgery, the ophthalmologist enters the patient's vision correction information in the excimer computer, and the excimer laser beam vaporizes the surface of the cornea up to a precise depth. The procedure is performed under a local anesthetic. The first excimer laser was approved by the U.S. Food and Drug Administration on October 20, 1995 for the treatment of mild to moderate nearsightedness (-1.5 to -7.0 diopters with astigmatism no greater than 1.5 diopters) in persons aged 21 or older. The approval was based on the results of clinical trials.
Laser Assisted In Situ Keratomileusis
LASIK combines PRK with elements of ALK. LASIK is considered most effective for patients with higher levels of myopia (up to -20 diopters). The ophthalmologist uses an automated microkeratome to shave off a thin, hinged layer of the cornea. The surgeon then uses the excimer laser to vaporize a thin layer of the underlying cornea, and the top flap is restored to its place. LASIK is the newest refractive procedure and therefore there is little hard data on its outcomes. However, many refractive surgeons believe LASIK holds the most promise for patients with moderate to high myopia. LASIK is under investigational trials in the United States.
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