Comparison of Ultrasound and Orbscan II in Measuring Central Corneal Thickness

To compare Orbscan II and ultrasonic pachymetry for measurement of central corneal thick-ness (CCT) in eyes scheduled for keratorefractive surgery. 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. 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. 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.