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Personalized nomogram can improve custom ablation outcomes
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WAILEA, Hawaii — Refractive surgeons can optimize their LASIK results and avoid systematic errors in their patients by adopting a personalized nomogram for custom ablation, according to a speaker here.
At Hawaiian Eye 2006, Yunhee Lee, MD, explained that even two surgeons with nearly identical surgical styles, using the same laser in the same laser suite, will have slightly different outcomes when using the same nomogram.
Dr. Lee said she and colleagues used regression analysis to analyze the results of conventional vs. customized LASIK, as well the results of customized LASIK performed by two surgeons using the same nomogram.
Graphed on a scatterplot, the outcomes of the two surgeons — both using the same customized laser platform, staff, laser suite and technical style — differed by approximately 0.75 D, she said.
“Indeed, the slopes of these scatter plots are not identical [as we expected], but differ by about 0.75 D, underscoring the need for personalized nomograms,” Dr. Lee said.
She recommended using one of the commercially available software packages for generating a personal nomogram, such as SPSS/SAS, Outcomes Analysis Software, Refractive Surgery Consultant 2000 or Refractive Surgery Consultant Elite.
In creating the personal nomogram, Dr. Lee suggested leaving out variable that are held constant from case to case, such as temperature and humidity, and choosing variables that change such as age, gender, keratometry and IOP.
“Variables that are held constant from case to case will not alter your outcome and will be one more variable you don’t have to track and analyze,” Dr. Lee said. “Anything you change from case to case could potentially be important in your outcome.”
Above all, she stressed the need to keep the nomogram simple and consistent. She said it is important to “not change things on the fly or month-to-month based on how you think things are going.”
Creating a personal nomogram sooner rather than later is advisable, she said, “to avoid systematic errors in large groups of people.”