comparison of ultrasound and orbscan ii in measuring central corneal thickness

purpose: to compare orbscan ii and ultrasonic pachymetry for measurement of central corneal thick-ness (cct) in eyes scheduled for keratorefractive surgery. methods: cct was measured using orbscan ii and then by ultrasonic pachymetry in 100 eyes of 100 patients who were scheduled for excimer laser refractive surgery. paired t-test was used for comparing the results. results: using an acoustic factor (af) of 0.92 for measurements by orbscan pachymetry, the difference between mean cct measured by ultrasound (544.7±35.5 μm) and orbscan (546.9±41.6 μm) was not statistically significant (p=0.14). the standard deviation of measurements was greater with orbscan pachymetry but this was not statistically significant. conclusion: cct measurements are comparable between orbscan ii (applying an af) and ultrasound pachymeter; however when cct measured by orbscan ii is in the lower ranges, it is better to recheck it using ultrasound pachymetry.