central corneal thickness measurements using galilei, orbscan ii, and ultrasonic pachymetry

purpose: to compare central corneal thickness (cct) measured by galilei and orbscan ii with that by ultrasonic (u/s) pachymetry in unoperated eyes. methods: cct was measured in 184 unoperated eyes of 92 healthy retractive surgery candidates using galilei, orbscan ii, and u/s pachymetry. considered as a benchmark, measurements by u/s pachymetry were compared to those obtained by the other two devices. agreement between the three instruments was assessed using regression analysis, mountain plots, and bland-altman plots. results: mean cct was 544.4±33.4 mm, 546.7±37.9 mm, and 555.8±29.6 mm as measured by ultrasonic pachymetry, orbscan ii, and galilei systems, respectively. mean differences between readings measured by u/s pachymetry and those measured by orbscan ii (acoustic coefficient 0.96) and galilei were 2.3 mm and 10.2 mm, respectively. despite this discrepancy, galilei had a better agreement with u/s pachymetry as compared to orbscan ii (correlation coefficient of 0.947 vs 0.817). considering acoustic coefficient of 0.98 for galilei, its cct readings were more similar to u/s pachymetry. conclusion: galilei is well correlated with u/s pachymetry for measurement of cct in normal eyes and by applying an acoustic coefficient of 0.98 for galilei, its records can be considered equivalent to u/s pachymetry. further investigations are required to address its accuracy in abnormally thin corneas such as corneal ectasia and after refractive surgeries.