Surgical Vision Correction (Refractive Surgery with the Excimer Laser)
Peter S. Hersh, MD
Laser vision correction (LASIK and PRK) is a relatively new procedure used to reduce or eliminate a person's dependence on glasses and contact lenses. The procedure is performed on an outpatient basis and is effective for treating nearsightedness, farsightedness, and astigmatism. To date, over two million procedures have been performed worldwide.
How Does the Laser Work?
The goal of excimer laser LASIK and PRK is to reshape the cornea so that the rays of light that enter the eye are focused clearly onto the retina. The laser produces an ultraviolet beam of light that meticulously removes tissue. Tissue is removed in a precise fashion on a microscopic level, without harming or heating adjacent corneal tissue. This process of tissue removal is calledphotoablation
In addition, the precision of the excimer laser makes it uniquely suited to the task of refractive corneal surgery. Each pulse of the laser removes only 0.25 microns of tissue (1/28 of a red blood cell) in four-billionths of a second. This allows the surgeon to safely sculpt the cornea into a more optically desirable shape, ultimately allowing the rays of light to focus properly on the retina.
How the Excimer Laser Corrects Vision
In actually applying the laser to the eye, the
Correction of Nearsightedness, Farsightedness, and Astigmatism
How Much Tissue Should be Removed?
The amount of tissue removed in each of these procedures is determined by the patient's degree of refractive error. Before the laser is used, the degree of refractive error is translated into numbers that are entered into the laser's computer. The quantity and pattern of tissue removal unique to each patient are then calculated. Both PRK and LASIK are refractive procedures that utilize the precision of the excimer laser to reshape the optical surface of the eye.