Intraocular Lens Power Calculation after Refractive Surgery: A Comparative Analysis of Accuracy and Predictability

Abstract

Purpose: To compare the accuracy of intraocular lens (IOL) power calculation using conventional regressionformulae or the American Society of Cataract and Refractive Surgery (ASCRS) IOL power calculator for previouscorneal refractive surgery. Methods: We retrospectively reviewed 96 eyes from 68 patients that had undergone cataract surgery afterkeratorefractive surgeries. We calculated the formula with two approaches: IOL powers using the ASCRSIOL power calculator and IOL powers using conventional formulae with previous refractive data (Camellin,Jarade, Savini, and clinical history method) or without prior data (0, 2 and, 4 mm total mean power in topography,Wang-Koch-Maloney, Shammas, Seitz, and Maloney). Two conventional IOL formulae (the SRK/T andthe Hoffer Q) were calculated with the single K and double K methods. Mean arithmetic refractive error andmean absolute error were calculated at the first postoperative month. Results: In conventional formulae, the Jarade method or the Seitz method, applied in the Hoffer Q formulawith the single K or double K method, have the lowest prediction errors. The least prediction error was foundin the Shammas-PL method in the ASCRS group. There was no statistically significant difference betweenthe 10 lowest mean absolute error conventional methods, the Shammas-PL method and the Barrett True-Kmethod calculated with using the ASCRS calculator, without using preoperative data. Conclusions: The Shammas-PL formula and the Barrett True-K formula, calculated with the ASCRS calculator,without using history, were methods comparable to the 10 most accurate conventional formulae. Othermethods using the ASCRS calculator show a myopic tendency.