Predicted vs measured posterior corneal astigmatism for toric intraocular lens calculations

Abstract

Purpose:To evaluate the astigmatic correction obtained with a toric intraocular lens using the keratometric readings (Ks) from a swept-source optical coherence tomography (SS-OCT) biometer and the Barrett toric formula with its predicted posterior corneal astigmatism (PCA) value and to compare the results with those expected by using the OCT Ks and a measured PCA from a scheimpflug topographer and by using the SimKs and the measured PCA from the Scheimpflug topographer.Setting:Private practice, Lynwood, California.Design:Retrospective observational study.Methods:All measurements were performed by the SS-OCT biometer and the Scheimpflug topographer and using the Barrett toric formula.Results:We evaluated 122 eyes of 122 patients. The mean absolute errors in predicted residual astigmatism for the entire series were 0.41 ± 0.19 diopters (D) (0.00 to 0.85 D) using the OCT Ks and predicted PCA, 0.45 ± 0.25 D (0.00 to 1.01 D) using the OCT Ks and measured PCA, and 0.49 ± 0.25 D (0.00 to 1.30 D) using the SimKs and measured PCA. The statistically significant differences between the errors had a P value of.062 for the entire series (n = 122),.26 for the subgroup with against-The-rule astigmatism (n = 68),.47 for the subgroup with oblique astigmatism (n = 11), and.05 for the subgroup with with-The-rule astigmatism (n = 43). The percentage of eyes within ±0.50 D were 74% (n = 90), 71% (n = 87) and 64% (n = 78) (P =.13) and within ±0.75 D were 99% (n = 121), 95% (n = 116) and 84% (n = 102) (P