Photorefractive Keratectomy Procedure

Some of the nearly 25% of Americans who are nearsighted are turning to a laser surgical technique known as photo-refractive keratectomy, or PRK, to improve their eyesight. The procedure uses an excimer laser to reshape the surface of the cornea--the eye’s clear protective covering--in order to improve the way light is focused by the eye. A look at how the treatment works:

1. A patient arriving for PRK surgery is given a tranquilizer, taken to the laser room and asked to recline in what resembles a dentist’s chair. The physician administers eyedrops to numb the surface of the eye.

2. The patient is told to focus on a flashing beam of light to ensure he or she look directly at the laser.

3. The doctor removes the epithelium--the cornea’s outermost layer. The physician then begins the PRK procedure by pushing down on a foot pedal to discharge the laser. A computer inside the laser machine, programmed with the patient’s eye measurements, guides the invisible ultraviolet beam.

4. When the laser hits the eye, a soft popping sound results. With each sound, caused by a pulse in the beam, about 100,000th of an inch is removed from the eye’s surface. The computer changes the pulse’s speed and the beam’s diameter to match the patient’s eye measurements.

5. The laser starts as a narrow beam and then widens, removing more tissue in the central portion of the cornea. The procedure, which takes about 20 seconds, flattens out the center of the cornea. In creating this flat surface, the laser is, in effect, sculpting the shape of a contact lens onto the surface of the eye, thereby correcting the patient’s vision.

6. Most patients will notice an immediate improvement in their vision. The physician puts a clear plastic lens over the eye as protection, which is removed a few days later.

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Myopia (nearsightedness)

Light rays focus in front of the retina instead of directly on it, causing nearsightedness.

Photorefractive Keratectomy

PRK allows light rays to focus more directly on the retina.