Relationship of corneal asphericity to intraocular lens power calculations after myopic laser in situ keratomileusis

PURPOSE: To examine whether corneal asphericity affects underestimation in the SRK/T intraocular lens (IOL) power calculation after myopic laser in situ keratomileusis (LASIK) and to evaluate the predictability of IOL power underestimation using the asphericity. SETTING: Kitasato University, Kanagawa, and Miyata Eye Hospital, Miyazaki, Japan. DESIGN: Retrospective case series. METHODS: The clinical records of eyes that had IOL implantation during cataract surgery after previous myopic LASIK between May 2008 and October 2014 were reviewed. For eyes with an available clinical history, the effect of manifest refraction spherical equivalent before LASIK, axial length, and the asphericity (Q value) on cataract surgery and the refractive error in the use of the SRK/T formula were examined using stepwise multiple regression analysis. Predictions with the resultant regression equation and significant factors were evaluated with Bland-Altman plots. RESULTS: Fifty-four eyes of 37 patients were included. The mean duration from LASIK to cataract surgery was 9.1 years +/- 3.5 (SD) (range 2 to 14 years). Multiple regression analysis using 22 eyes of 22 patients resulted in a significant factor, which was the Q value (P < .001, R-2 = 0.80). The refractive errors in 53 eyes were predicted with tolerances of 64.5% and 87.0% within +/- 0.5 diopter (D) and within +/- 1.0 D, respectively. Bland-Altman analysis showed that 95% of the limitation range was 2.59 D. CONCLUSIONS: The corneal asphericity after myopic LASIK significantly correlated with the IOL power underestimation with use of the SRK/T formula. The refractive error could also be predicted well with the use of asphericity.