| Wizkid 2004-10-29, 7:16 pm |
| TOP STORIES 10/24/2004
ALTITUDE AFFECTS LASIK NOMOGRAM
NEW ORLEANS — Altitude has a linear effect on the laser performance in
LASIK, requiring a greater nomogram adjustment at higher elevations,
according to a study that looked at data from centers across the
United States. Louis Probst, MD, discussed the findings of the study
here at the American Academy of Ophthalmology meeting.
Dr. Probst, one of the directors of the laser center chain TLC Vision,
analyzed data from 13 centers spanning 2 years. To be included in the
analysis, each center had to perform more than 1,000 surgeries during
that time period, he said. The personalized nomogram adjustments used
by each center for correction of myopia between 3 D and 6 D were
compared using regression analysis.
All centers had standardized temperature and humidity controls,
leaving altitude as the sole variable in atmospheric pressure, Dr.
Probst said.
The analysis showed a relationship – "not a tight relationship, but
linear" – between altitude and the nomogram reduction factor used in
each center, Dr. Probst said.
The reduction factor varied from 0.7% at sea level to 12.7% at 1,000
feet elevation to 34.9% at 3,000 feet, he said.
Taking altitude into account may help surgeons in developing and
adjusting their own nomograms for LASIK, Dr. Probst suggested.
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