|Richard A. Eiferman, M.D., F.A.C.S
Corneal Surgery and External Eye Disease
Springs Medical Center
6420 Dutchman's Parkway, Suite 170
Louisville, KY 40205
(502) 895-4200, Fax (502) 895-0819, 24 HOUR ANSWERING SERVICE
|The excimer laser is a revolutionary tool for
performing refractive surgery. Since the cornea absorbs all ultra-violet wavelengths, a
high energy Argon-Fluroide UV laser is used to cleave the carbon-carbon bonds of the
cornea. This causes instantaneous vaporization of the superficial cornea with essentially
no effect on the subjacent tissue. When controlled by a sophisticated computer program,
the surgery is exquisitely precise; each pulse can remove .1 micron in a billionth of a
second. No incisions are made; refractive errors are corrected by actually reshaping the
front surface of the eye. In essence, the patient's contact lens prescription is sculpted
directly onto the cornea. The excimer laser is capable of correcting higher amounts of
nearsightedness as well as astigmatism and farsightedness.
Radial keratotomy has been evolving for twenty years and it should be emphasized that excimer laser ophthalmic surgery is still in its infancy. A "second generation" scanning excimer laser has now become available and clinical trials are underway at Suburban Medical Center. "Third generation" solid state lasers are being developed using different wavelengths and delivery systems. The clinical studies indicate that RK and the excimer are probably equivalent for small amounts of nearsightedness. However, a few caveats must be mentioned. RK incisions extend 90 percent through the cornea with permanent weakening and a predisposition to rupture with trauma. A more insidious complication is progressive farsightedness; some patients actually continue to have a further effect from their surgery years after the procedure. Finally, some patients have "starburst" images caused by light. reflecting from the ends of their incisions.
After six years of clinical trials, the excimer laser was approved by the FDA in 1996 for treatment of myopia between -1:00 and -16.00 diopters. The laser is also now approved for astigmatism and farsightedness.
In countries that are unhindered by governmental agencies, the excimer laser has virtually replaced RK as the procedure of choice for refractive surgery. I believe the same situation will occur in the United States.