ROCHESTER, Minn. May 03, 2006 -- A Mayo Clinic study comparing
femtosecond (bladeless) and mechanical microkeratome LASIK surgeries
has found equal results from both types six months post-surgery,
using a variety of vision and eye health measurements. The study's
findings will be presented next week in three abstracts at the Association
for Research in Vision and Ophthalmology meeting in Fort Lauderdale,
Fla. LASIK (Laser-assisted in situ keratomileusis) involves treating
nearsightedness, farsightedness or astigmatism by reshaping the
eye's cornea to alter the way the eye refracts light. LASIK involves
creating a flap, removing a defined amount of corneal tissue by
an excimer laser, and replacing the flap. In standard LASIK with
a mechanical microkeratome, the flap is created by a blade; in bladeless
LASIK, the newer type, the flap is created by a femtosecond laser.
"At six months after surgery, there are no differences between
the eyes that had bladeless or microkeratome LASIK with respect
to visual acuity (vision as measured by reading an eye chart), contrast
sensitivity (ability to discriminate bright objects from dark objects),
or in perception of stray light or glare, such as the glare from
oncoming headlights," says Sanjay Patel, M.D., Mayo Clinic ophthalmologist
and study investigator.
Given the equivalent findings thus far in eye health and vision
between the two types of LASIK, Dr. Patel slightly prefers bladeless
LASIK due to its potential safety, which was not measured in his
study. "I'd say the short-term outcomes are equal and the risks
are, in theory, less with the bladeless technique, although our
study was not designed to compare risks," he says. "Bladeless LASIK
is potentially safer because of its computer-controlled precision,
the ability to visualize the flap being created, and to stop the
procedure whenever necessary. That said, however, the risk of complications
with a traditional, microkeratome blade is very small: some vision
loss from surgery with a microkeratome blade occurs in well under
1 percent of all cases. The long-term risks of either procedure,
however, are unknown, and defining them is the primary purpose of
our study."
The study followed 20 patients who received LASIK for nearsightedness
or astigmatism. Each patient was treated with microkeratome LASIK
in one eye and bladeless LASIK in the other eye. The researchers
found no difference in subbasal nerve density between types of surgery,
though the density decreased after both treatments compared to density
before LASIK. Corneal sensitivity did not differ between microkeratome
and bladeless LASIK. Subbasal nerve density and corneal sensitivity
do not impact vision, but rather the potential to heal from a scratch
or other injury to the eye. High-contrast visual acuity, the capability
to see fine details, and contrast sensitivity, the ability to perceive
contrast in objects and their environments, also did not differ
between LASIK types. The researchers found corneal backscatter was
greater with bladeless LASIK for the first three months after surgery,
yet the patients perceived no difference in vision after three months
between their eyes treated with bladeless or microkeratome LASIK.
Backscatter is haziness in the cornea that is usually invisible
to the naked eye and is identified through testing in a physician's
office. Cell densities in all layers of the cornea also did not
differ between the LASIK surgeries.
The ultimate goal of the Mayo Clinic study of microkeratome versus
bladeless LASIK is to obtain long-term information about patients'
vision and eye health five years following surgery. The results
presented now represent the first six months of findings.
Other Mayo Clinic researchers involved in this study include:
Cherie Nau; Jay McLaren, Ph.D.; Jay C. Erie, M.D.; Leo Maguire,
M.D.; and William Bourne, M.D. None of the investigators has any
commercial interests. The study was funded by the National Institutes
of Health, Research to Prevent Blindness, and Mayo Clinic. To obtain
the latest news releases from Mayo Clinic, go to www.mayoclinic.org/news.
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