Performance of the Barrett Toric Calculator with and without measurements of posterior corneal curvature

Abstract

Background: Toric intraocular lens power calculators, e.g., the Barrett Toric Calculator, based on predicted, rather than on measured posterior corneal curvature have yielded the best results so far. However, recent update of the Barrett Toric Calculator aims to fine tune its refractive predictions with the input of measured posterior corneal curvature. Here, we wanted to compare refractive predictions of the Barrett Toric Calculator, based on IOL Master 700 biometry, with and without measurements of posterior corneal curvature.

Methods: In total 30 eyes were included in the study. One-month postoperative manifest refraction and predicted residual refractive error of both formulas were utilized to calculate mean absolute error and centroid error in predicted residual astigmatism. The Pentacam was used to measure posterior corneal curvature.

Results: We did not find any statistically significant difference in mean absolute error and centroid error in predicted residual astigmatism between the Barrett Toric Calculator with and without measurement of posterior corneal curvature. Post-hoc analysis of with-the-rule and against-the-rule astigmatic eyes did not reveal any significant differences as well.

Conclusions: Astigmatism prediction errors, based on IOL Master 700 biometry, with and without measured posterior corneal curvature, were similar. To the best of our knowledge, the updated Barrett Toric Calculator is the first formula to provide non-inferior and reliable predictions based on measurement of posterior corneal curvature.

Fig. 1

Double-angle diagrams illustrating centroid errors in predicted residual astigmatism for the Barrett Toric calculator with a predicted posterior corneal astigmatism and b measured posterior corneal astigmatism (PCA)

Fig. 2

Double-angle diagrams illustrating centroid errors in predicted residual astigmatism in eyes with against-the-rule (ATR) astigmatism for the Barrett Toric calculator with a predicted posterior corneal astigmatism and b measured posterior corneal astigmatism (PCA)

Fig. 3

Double-angle diagrams illustrating centroid errors in predicted residual astigmatism in eyes with with-the-rule (WTR) astigmatism for the Barrett Toric calculator with a predicted posterior corneal astigmatism and b measured posterior corneal astigmatism (PCA)