title: Central Corneal Thickness Measurement by Ultrasound versus Orbscan II.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Ophthalmic Research Center, Labbafinejad Medical Center, Shahid Beheshti University MC, Tehran, Iran.
authors.forename: Amir
authors.initials: A
authors.lastname: Faramarzi
authors.forename: Hossein
authors.initials: H
authors.lastname: Ziai