Comparison of the Barrett toric calculator using measured and predicted posterior corneal astigmatism and the Kane and Abulafia-Koch calculators

Purpose: To compare the accuracy of the Barrett toric calculator with measured and predicted posterior corneal astigmatism (MPCA and PPCA, respectively), the Abulafia-Koch (AK) formula, and the toric Kane formula. Setting: Ein-Tal Eye Center, Tel-Aviv, Israel. Design: Retrospective cohort. Methods: Consecutive cases of patients who underwent uneventful cataract extraction surgery with implantation of a toric intraocular lens between March 2015 and July 2019 were retrospectively reviewed. 1 eligible eye from each patient was included. The predicted postoperative refractive astigmatism was calculated using each method and compared with the postoperative refractive astigmatism to give the prediction error. Results: 80 eyes of 80 patients were included in this study. Themean centroid and the mean and median absolute prediction errors using Kane (0.25 diopters [D] +/- 0.54@ 6 degrees, 0.50 D +/- 0.31 and 0.45 D, respectively) were significantly different compared withMPCA(0.12D +/- 0.52 @ 16 degrees, P <.001,.44 D +/- 0.28 and 0.36 D, P =.027, respectively), PPCA (0.09 D +/- 0.49 @ 12 degrees, P <.001,.41 D +/- 0.27 and 0.35 D, P <.001, respectively), and AK (0.11 D +/- 0.49 @ 11 degrees, P <.001,.42 D +/- 0.27 and 0.35 D, P =.004, respectively). No significant differences were found between the calculators in the predictability rates within +/- 0.25 D, +/- 0.50 D, +/- 0.75 D, and +/- 1.00 D. Conclusions: The measured posterior corneal curvature in the Barrett calculator yielded comparable outcomes to its prediction by the Barrett and AK formulas. The Kane calculator showed a slight against-the-rule prediction error compared with the other methods, resulting in a small higher median absolute error with marginal clinical importance.