Clinical reliability of the topolyzer vario instrument for measurement of corneal refractive power

Purpose: To evaluate the clinical reliability of the Topolyzer Vario (Wavelight-Alcon, Erlangen, Germany), we compared three different corneal topographers in terms of corneal refractive power. Methods: The medical records of patients who visited Severance Hospital for corneal refractive surgery were retrospectively reviewed. Keratometric data of patients who underwent evaluations using the Pentacam HR (Oculus, Wetzlar, Germany), ORBscan II (Bausch & Lomb, Rochester, NY, USA), and Topolyzer Vario instruments on the same day were obtained. Flat keratometry (Kf), steep keratometry (Ks), mean keratometry (Km), astigmatism keratometry (Kastig), Cartesian astigmatism (J0), and oblique astigmatism (J45) values were calculated. The measurement values of the three devices were subjected to Pearson's correlation analysis and repeated measures analysis of variance (with Bonferroni correction); a Bland-Altman plot was also created. Results: The keratometric data of 80 eyes were included in the analysis and all of the keratometric measurements obtained by the three devices showed significant correlations, i.e., good agreement. The Kf and Km measurements of the Pentacam HR were flatter than those of the ORBscan II, and the Kf, Km, Ks, and J45 measurements were flatter than those of the Topolyzer Vario. However, there was no significant difference in keratometric values between the ORBscan II and Topolyzer Vario. Furthermore, the difference in corneal refractive power between the Pentacam HR and Topolyzer Vario was not clinically significant. Conclusions: When measuring the corneal refractive power of patients without any history of corneal disorder or ocular surgery, the Topolyzer Vario is a clinically reliable device that shows similar performance to the ORBscan II and Pentacam HR.