LASIK being tested as treatment for farsightedness
BY RUTHANN RICHTER
Ophthalmologists at Stanford have begun a clinical trial of a new laser treatment to correct vision in people who are naturally farsighted, with or without astigmatism, or who have become farsighted as a result of earlier eye surgeries. The trial is believed to be one of the first in the United States to test the value of the technique in patients with these vision problems, said Edward Manche, MD, assistant professor of ophthalmology and director of refractive surgery.
The technique is called LASIK, or laser in-situ keratomileusis.
"There were many people who had radial keratotomy [RK] and who are farsighted because of the unrecognized consequences of the progression toward farsightedness. Up until now, there was nothing we could offer them. This offers a solution to patients who have had RK in the past and are farsighted as a result," said Manche, the principal investigator in the new trial.
Radial keratotomy is a once-popular procedure in which doctors reshaped the cornea through a series of tiny incisions. The technique faded from the scene with the advent, in 1985, of the excimer laser, now the tool of choice for refractive surgeons, Manche said. In the meantime, however, thousands of once-nearsighted patients developed farsighted vision as a result of overcorrection by RK, he said.
Patients who have become farsighted as a result of newer procedures performed with lasers, such as photo-refractive keratectomy (PRK) and LASIK, are also eligible for the new trial, as are people with farsightedness and astigmatism (an unequal curvature of the eye that leads to blurred vision).
Manche has Food and Drug Administration approval to treat 200 patients in the study. A dozen patients already have undergone the LASIK procedure at Stanford as part of the trial, which began in July, he said.
The new technique was introduced in the United States in the early 1990s and is now the preferred approach for correcting nearsightedness, Manche said. Studies conducted in Europe and South America suggest that the technique may benefit farsighted patients as well, prompting a faster recovery and more stable results than PRK.
PRK is a similar laser procedure that has been used experimentally to correct farsightedness, said Manche, who took part in a recent national study of the approach.
"In our previous study [with PRK], we found that the body tended to reverse the effects of the laser," Manche said. "The more advanced [LASIK] technique has been shown in some international studies not to have the same problem."
About 20 percent of the U.S. population is farsighted, or hyperopic, he said. In these individuals, the light rays from a distant object are focused to a point behind the retina, and the result is a blurred image. In the LASIK procedure, Manche reshapes the cornea with an excimer laser to make it slightly steeper, rather than flat. This brings the light to focus directly on the retina.
During the procedure, he gently lifts aside a thin flap of tissue from the top layer of the cornea to expose the tissues beneath the surface. These tissues then are exposed to the ultraviolet light and high-energy pulses of the laser for 15 to 60 seconds. The flap then is moved back in its original place.
The excimer laser is a "cold" or nonthermal laser that breaks molecular bonds within cells to remove tissue. Because it does not produce heat, damage to surrounding tissue is minimal, Manche said. Patients receive an anesthetic eyedrop to numb the area and have reported that they feel no discomfort during the process, he said.
The LASIK technique differs from PRK in that surgeons using LASIK do not operate on the surface of the cornea and thus do not permanently destroy that surface layer of tissue, which does not regenerate, Manche said. Performing the work below the surface level reduces the chance of scarring and complicating vision problems, he said.
James Kadow, a junior high school teacher in Fremont, said he opted for the procedure this summer after years of living with near-blindness in one eye. He described the procedure as "interesting and unusual, but not at all painful or uncomfortable." As Kadow experienced it, "there's a pressure sensation, and you concentrate on looking at a little light." The process took no more than 20 minutes from start to finish. The following morning, he awoke and found himself able to see the world without reaching for his thick lenses, he said.
Manche said the risks involved in the procedure are primarily those associated with creating the flap, which can be too thick, too thin, irregular in shape or accidentally removed. The technique also carries a small risk of scarring, inflammation and infection, he said.
The Stanford trial is
self-supported, with patients paying $2,500 per treated eye, Manche