Accuracy of Ten Intraocular Lens Formulas in Spherical Equivalent of Toric Intraocular Lens Power Calculation

The aim of this work is to evaluate the accuracy of the Barrett Universal II (BU II), Emmetropia verifying optical (EVO) 2.0, Haigis, Hoffer Q, Hoffer QST (Savini/Taroni) (HQST), Holladay 1, Kane, Ladas Super, Sanders–Retzlaff–Kraff/theoretical (SRK/T), and T2 intraocular lens (IOL) power formulas for calculating spherical equivalent (SE) of toric IOL. This study enrolled consecutive patients who underwent phacoemulsification and toric IOL implantation at the Eye Hospital of Wenzhou Medical University in Hangzhou from 2015 to 2022. We compared the new-generation formulas with Gaussian optics-based standard formulas, and calculated the mean absolute error (MAE), median absolute error (MedAE), and percentage of eyes within ± 0.25 diopter (D), ± 0.50 D, ± 0.75 D and ± 1.00 D of the target refraction. Subgroup analyses were conducted based on the anterior chamber depth (ACD), keratometry (K), and toricity (T). A total of 207 eyes of 207 patients were included in this study. Overall, the Kane and EVO2.0 formulas demonstrated the lowest MedAEs. The EVO2.0 formula exhibited the highest percentage of eyes within ± 0.50 D, ± 0.75 D, ± 1.00 D. Moreover, the EVO2.0 formula showed the lowest MedAE for flat K subgroup, the highest percentage of eyes within ± 0.50 D, ± 1.00 D for shallow ACD subgroup, the highest percentage of eyes within ± 0.75 D for regular ACD, flat K, T2–T3, T4–T5 subgroups. The Kane and formula performed the lowest MedAE in the T4–T5 subgroup. Application of the Kane and EVO2.0 formulas significantly improved the prediction of postoperative SE outcome for toric IOL compared to the other formulas.