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 said. SR
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