Corneal Refractive Power Estimation and Intraocular Lens Calculation after Hyperopic LASIK

Purpose: To identify key independent variables in estimating corneal refractive power (KBC) after hyperopic LASIK. Design: Retrospective study. Participants: We included 24 eyes of 16 hyperopic patients who underwent LASIK with subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation in the same eye. Methods: Pre-LASIK and post-LASIK spherical equivalent (SE) refractions and topographies, axial length, implant type and power, and 3-month postphacoemulsification SE were recorded. Using the double-K Hoffer Q formula, corneal power was backcalculated for every eye (KBC), regression-based formulas derived, and corresponding IOL powers calculated and compared with published methods. Main Outcome Measures: The Pearson correlation coefficient (PCC) and arithmetic and absolute corneal and IOL power errors. Results: Adjusting either the average central corneal power (ACCP_3mm) or SimK based on the laser-induced spherical equivalent change (ΔSE) resulted in an estimated corneal power (ACCP_adj and SimK_adj) with highest correlation with KBC (PCC = 0.940 and 0.956, respectively) and lowest absolute corneal estimation error (0.37±0.45 and 0.38±0.39 diopter [D], respectively). The ACCP_adj closely mirrored published ΔSE-based adjustments of central corneal power on different topographers, whereas ΔSE-based SimK adjustments varied across platforms. Using ACCP_adj or SimK_adj in the double-K Hoffer Q, using ACCP_3mm or SimK in single-K Hoffer Q and adjusting the resultant IOL power based on ΔSE, or applying Masket's formula all yielded accurate and similar IOL powers. The Latkany method consistently underestimated IOL power. The Feiz-Mannis and clinical history methods yielded poor IOL correlations and large IOL errors. Conclusion: After hyperopic LASIK, adjusting either corneal power or IOL power based on ΔSE accurately estimates the appropriate IOL power. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references.