Accuracy of Toric Intraocular Lens Formulas in Eyes With Previous Myopic Laser Vision Correction

Purpose: To compare the refractive prediction accuracy of two modern toric intraocular lens power formulas, using predicted or measured posterior corneal astigmatism, in eyes with a history of previous myopic laser vision correction (LVC). Methods: This retrospective case series included 182 eyes with a history of previous myopic LVC that underwent uncomplicated cataract surgery with implantation of a monofocal non-toric IOL. Preoperative biometry was performed with swept-source optical coherence tomography. Spherical equivalent and refractive astigmatism prediction accuracy of the Barrett True K Toric and Emmetropia Verifying Optical (EVO) Toric formulas, using predicted posterior corneal astigmatism (PPCA) or measured posterior corneal astigmatism (MPCA), was analyzed using vector analysis and the Eyetemis online tool ( https://eyetemis.com/ ). Results: For spherical equivalent prediction accuracy, the EVO Toric formula with MPCA had the highest proportion of eyes within ±0.50 diopters (D) (68%) and the lowest mean absolute error (0.419 D). The trimmed mean spherical equivalent prediction error for Barrett True K MPCA was significantly smaller than for Barrett True K PPCA ( P < .01). With respect to refractive astigmatism, there was no significant difference in the absolute refractive astigmatism prediction error for EVO PPCA compared to EVO MPCA ( P = .89). However, the refractive astigmatism prediction error for Barrett PPCA was smaller than for Barrett MPCA ( P < .01). Conclusions: Measured posterior corneal astigmatism improves the prediction accuracy of both the EVO and Barrett True K toric formulas with respect to the spherical equivalent but has a detrimental effect on the refractive astigmatism prediction accuracy of the Barrett True K toric formula.