This article is more than 5 years old. Information may no longer be current.
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.