LASIK in Summer, Think Twice
Warm temperatures and high humidity increase the need
for follow-up procedures after LASIK surgery.
Quote: "Our study doesn't
mean that consumers should avoid LASIK surgery during the summer," said Dr.
Keith Walter, author of the study. "But they should make sure that their
physicians compensate for temperature and
humidity."
Comment: How are consumers supposed to "make sure that their
physicians compensate for temperature and humidity"?
Barbara K. Hecht,
Ph.D.
Frederick Hecht, M.D.
Medical Editors, MedicineNet.com
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Temperature and Humidity Can Affect LASIK Surgery Results
Winston Salem, N.C. - Humidity and temperature levels can affect LASIK
surgery results, increasing the number of people who need follow-up procedures,
report researchers from Wake Forest University Baptist Medical Center.
"This is the first study to show that environmental factors can affect
LASIK outcomes," said Keith Walter, M.D., assistant professor of
ophthalmology. "For best results,
physicians should take these factors into account when calibrating laser
equipment."
The results are reported in the current issue of the
Journal of Cataract and
Refractive Surgery.
Walter found that a 10 percent increase in treatment room humidity meant an
additional nine out of every 100 patients required an enhancement procedure.
Results also were influenced by outdoor temperatures and humidity in the weeks
before surgery, said Walter, with more enhancement surgeries required during the
humid summer months.
The number of eyes requiring an enhancement procedure ranged from 0 percent
in the winter months to 50 percent in September, when outdoor humidity was at
its highest. During less-humid months, there was a tendency to overcorrect
vision. During the more humid summer months, there was a tendency toward
undercorrection.
In the study of 191 patients, Walter evaluated 12 variables that were
suspected to affect LASIK results. These factors included age, sex,
environmental factors such as room and outdoor temperature, and curvature of the
cornea, the clear, front part of the eye that provides most of the focusing
power.
LASIK, which stands for Laser-Assisted In Situ Keratomileusis, is a procedure
that permanently changes the shape of the cornea using an ultraviolet laser.
"The goal of LASIK should be for a maximum number of patients to achieve
eyeglass-free vision with a single procedure," said Walter. "This study
evaluated environmental variables that may influence outcomes."
Walter performed the surgery on 368 eyes, with an
average of 15.5 percent requiring a second procedure to fine-tune vision. An
analysis of the variables showed that indoor humidity had the largest impact on whether enhancement
surgery was required. But, outdoor temperature and humidity in the two weeks
before surgery also played a role.
Walter said additional moisture in the air may decrease the laser energy
absorbed by the stroma, the
thickest layer of tissue in the cornea. Also, some
patients' corneas may become more hydrated before the procedure, making it
more difficult for the laser to remove tissue.
"Environmental data should play a role in how the equipment is programmed
to further refine the visual outcome," said Walter. He has developed a formula
for programming the equipment at Wake Forest, and has already seen improved
results.
"Our study doesn't mean that consumers should avoid LASIK surgery during
the summer," said Walter. "But they should make sure that their physicians
compensate for temperature and humidity."
Walter's co-researcher was Aaron W. Stevenson, a medical student at Wake
Forest.
Source: Wake Forest University Baptist Medical Center press release, April 20,
2004
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