FEB 12, 2008
By Jack Singer, MD
Cataract/Anterior Segment
A recent study in the Journal of Cataract & Refractive Surgery offers yet another option for calculating post-LASIK IOL power. It evaluates the accuracy of a new technique, consensus K, and found that it yielded refractive outcomes similar to a control group of patients who never had LASIK surgery. And it generated better outcomes than all other K or IOL-generating techniques, with the exception of the classic refractive history method.
The consensus-K technique described in this study uses the following methods to determine K values in patients who had previous LASIK:
- Refractive history
- Contact Lens
- Manual K
- Hamed
- Shammas I & II
- Maloney
- Videokeratography
These K-values were compared for agreement between methods. The outlier values (more than 1.5 D higher or lower than the mean value) were eliminated. The consensus K-value was chosen based on the average of remaining values within 0.75 D of each other.
This technique yielded better results than any of the individual techniques utilized to generate the consensus K. In addition, four IOL-generating methods (corneal bypass, double-K, Feiz-Mannis 1, and Feiz-Mannis 2) were compared to the IOL generated using the consensus-K value in the SRK/T formula, and a greater variability in the ranges of each method compared with the consensus-K method was found.
Among this study's limitations, it did not indicate if patients had previous myopic or hyperopic LASIK. It also didn't include a comparison to the Haigis-L formula, the Masket regression formula or the Pentacam Holladay Report.
ASCRS has posted on its Web site a valuable took for IOL power calculation in eyes with prior myopic LASIK or PRK, prior hyperopic LASIK or PRK, or prior RK. It maximizes the number of formulas you can use with the data you have available. It can be found at http://iol.ascrs.org/.