A new review of recent studies suggests two popular laser-assisted surgeries
to correct nearsightedness are equally effective at restoring 20/20 vision six
months to a year after the surgery.
However, LASIK patients tend to recover their vision faster than PRK
patients, which may be part of the reason their number has grown rapidly since
the late 1990s, said Dr. Alex Schortt and Dr. Bruce Allan of the Moorfields Eye Hospital
LASIK patients also report less pain after surgery than PRK patients,
although they tend to be more uncomfortable during the actual surgery, the
Schortt says patients might prefer these "side effects" associated with
LASIK, but "none of the individual studies included in this review demonstrated
a significant [vision] advantage for either treatment," he said.
"There are cases for both procedures where LASIK would be best for one
patient and PRK would be best for another patient," said Melissa Bailey, Ph.D.,
an optometrist at the Ohio State University College of Optometry. "It really
depends on individual patient factors," such the thickness of tissues in the eye
and severity of the nearsightedness, she said.
The review appears in the current issue of The Cochrane Library, a
publication of The Cochrane Collaboration, an international organization that
evaluates medical research. Systematic reviews draw evidence-based conclusions
about medical practice after considering both the content and quality of
existing medical trials on a topic.
Typically, the nearsighted eye is longer than usual from back to front. This
shape causes the eye to focus on light from distant objects in front of instead
of directly on the retina, the part of the eye that transforms light into the
nervous system signals that make up vision. The misfocus blurs the appearance of
far-off objects such as highway signs or faces seen at a distance in a crowd.
LASIK (laser-assisted in-situ keratomileusis) and PRK (photorefractive
keratectomy) both use a laser to reshape the eye's cornea, which helps to focus
incoming light, in people with nearsightedness. With PRK, the cornea is reshaped
by using the laser to gently shave off microscopic layers of the cornea. In
LASIK procedures, surgeons cut a flap in the cornea to remove excess tissue
below and then replace the flap like a hinged door.
In their review of six high-quality studies comparing LASIK and PRK, Schortt
and Allan found no significant difference in the number of eyes regaining 20/20
"perfect" vision six to 12 months after each type of surgery, regardless of how
severe the nearsightedness was before surgery. The studies involved a total of
417 eyes, 201 treated with PRK and 216 treated with LASIK, with some
participants having surgery only on one eye, or some having each eye treated
with the different procedures.
The researchers found some evidence that a greater proportion of eyes lose
some of their visual acuity with PRK compared to LASIK six months after surgery.
Vision lost after PRK may be due in part to a corneal "haze" produced by
inflammation caused by the procedure, the reviewers say.
"The risk of significant haze after PRK is an important difference between
these procedures," Schortt said, although he notes that none of the studies they
reviewed included the use of an anti-scar drug called mitomycin C, which has
been used successfully to cut back on postoperative eye haze.
Although Schortt and Allan said their conclusions are not new and are
"consistent with current practice," they believe that patients should still be
aware of how the procedures compare. Allan, a practicing surgeon, uses both
LASIK and PRK with his patients.
"I think patients and doctors prefer LASIK to PRK because it has a shorter
and less painful recovery time," Bailey said.
"These interventions are performed on healthy eyes and the vast majority of
patients are under 60 years of age," Schortt said, noting that patients can
still choose more conservative options such as glasses and contact lens to treat
It is important that patients are informed about and understand the
effectiveness, limitations, safety, complications and relative merits of these
procedures," he said.