Central Corneal Thickness Measurement by Ultrasound versus Orbscan II

Purpose: to compare orbscan ii and ultrasonic pachymetry for measurement of central corneal thickness (cct) in eyes scheduled for keratorefractive surgery. methods: cct was measured using orbscan ii (bausch & lomb, usa) and then by ultrasonic pachymetry (tomey sp-3000, tomey ltd, japan) in 100 eyes of 100 patients with no history of ocular surgery scheduled for excimer laser refractive surgery. results: mean cct was 544.7±35.5 (range 453-637) µm by ultrasonic pachymetry versus 546.9±41.6 (range 435-648) µm measured by orbscan ii applying an acoustic factor of 0.92 (p=0.14). the standard deviation of measurements was greater with orbscan pachymetry but the difference was not statistically significant. conclusion: cct measurements by orbscan ii (applying an acoustic factor) and by ultrasonic pachymetry are not significantly different; however, when cct readings by orbscan ii are in the lower range, it is advisable to recheck the measurements using ultrasonic pachymetry.