Evaluation of different IOL calculation formulas of the ASCRS calculator in eyes after corneal refractive laser surgery for myopia with multifocal IOL implantation

PURPOSE: To compare the accuracy of different intraocular lens (IOL) calculation formulas available on the American Society of Cataract and Refractive Surgery (ASCRS) post-refractive surgery IOL power calculator for the prediction of multifocal IOL power after previous corneal refractive laser surgery for myopia. METHODS: An analysis and comparison were performed of the accuracy of three methods using surgically induced change in refraction (ie, Masket, Modified Masket, and Barrett True-K formulas) and three methods using no previous data (ie, Shammas, Haigis-L, and Barrett True-K No History formulas). The average of all formulas was also analyzed and compared. RESULTS: Thirty-six eyes of 36 patients were included. All formulas, except for the Masket, Modified Masket, and Barrett True-K formulas, had myopic mean numerical errors that were significantly different from zero (P ≤ .01). The median absolute error of the Shammas formula (0.52 diopters [D]) was significantly higher compared to all of the other formulas (P < .05), except for the Haigis-L formula (P = .09). Comparing the formulas using no previous data, the Barrett True-K No History formula had the lowest median absolute error (0.33 D, P < .001). CONCLUSIONS: The Shammas formula showed the least accuracy in predicting IOL power in eyes with multifocal IOL implantation after previous corneal refractive laser surgery for myopia. In eyes with all available data, all formulas performed equally except for the Shammas formula, whereas in eyes lacking historical data, the Barrett True-K No History formula performed best