Comparison of SRK/T and Haigis formulas for predicting corneal astigmatism correction with tonic intraocular lenses

Abstract

PURPOSE: To compare the accuracy of the SRK/T and Haigis formulas for predicting corneal astigmatism correction with a toric intraocular lens (IOL). SETTING: Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea. DESIGN: Retrospective cross-sectional study. METHODS: Eyes with an Acrysof toric IOL were enrolled in the study. The corneal plane effective cylinder power of toric IOLs (target induced astigmatism vector [TIA]) predicted by the SRK/T and Haigis formulas were compared with the cylindrical correction achieved postoperatively (surgically induced astigmatism vector [SIA]). The magnitude of error was defined as the difference between the magnitudes of the SIA and TIA. The median absolute magnitudes of error predicted by the SRK/T and Haigis formulas were compared. The median absolute errors predicted by the 2 formulas were also compared. RESULTS: The mean postoperative SIA was 1.80 diopters (D) +/- 0.55 (SD). The magnitude of error predicted by the SRK/T and Haigis formulas was 0.31 +/- 0.40 D and 0.23 +/- 0.40 D, respectively. The median absolute magnitude of error predicted by the Haigis formula was statistically significantly smaller than that predicted by the SRK/T formula (P<.001). The median absolute error predicted by the Haigis formula (0.35 D) was also statistically significantly smaller than that predicted by the SRK/T formula (0.43 D) (P=.003). CONCLUSION: The Haigis formula was more accurate than the SRK/T formula not only in predicting the refractive outcome but also in predicting corneal astigmatism correction by toric IOLs. (C) 2015 ASCRS and ESCRS