Agreement in central corneal thickness measurement between Corvis ST and ocular response analyzer

Purpose To evaluate the agreement and interchangeability of noncontact devices of ocular response analyzer (ORA) and the Corvis ST in central corneal thickness measurement. Methods In this prospective comparative study, central corneal thickness (CCT) readings of 284 healthy, nonglaucoma subjects, without previous ocular surgery, were measured with ORA and Corvis ST. Only data from right eyes were analyzed. The mean values of CCT measurements by the ORA versus Corvis ST were compared with the paired sample t test. Bland-Altman plots and 95% limits of agreement (95% LOA) were used to assess the agreement between the measurements of the two devices. Results The mean (+/- standard deviation) age of the participants was 28.0 +/- 4.9 years, and 36.6% were male. The mean CCT measurements were 555 +/- 32 mu m by the ORA and 536 +/- 32 mu m with the Corvis ST (P < 0.001). The Pearson correlation coefficient was 0.964 (P < 0.001). The 95% LOA between the ORA and the Corvis ST was 2.2 to 35.9 mu m. Conclusions The ORA measured the CCT up to 35.9 mu m greater than Corvis ST. Therefore, the two devices may not be used interchangeably for measuring CCT.