title: Central and peripheral corneal thickness measurement in normal and keratoconic eyes using three corneal pachymeters.
abstract: OBJECTIVE
  To assess the agreement among ultrasonic pachymetry, the Galilei dual Scheimpflug analyzer, and Orbscan II for central and peripheral (Galilei vs. Orbscan) corneal thickness (CCT and PCT) measurement in normal and keratoconic eyes.
  
  
  METHODS
  In this prospective study, CCT and PCT were measured in 88 eyes of 88 refractive surgery candidates and 128 eyes of 69 keratoconic patients with ultrasonic pachymetry, the Galilei, and Orbscan II. The readings by the three instruments were compared using one-way analysis of normal variance. Agreement among the three devices was assessed using Pearson and intraclass correlation coefficients, and Bland-Altman plots. The same analyses were employed to evaluate agreement between Galilei and Orbscan II for PCT measurement.
  
  
  RESULTS
  In the normal group, mean CCT was 551.0±39.4, 566.9±33.5, and 565.5±40.9 μm measured by ultrasonic pachymetry, the Galilei, and Orbscan II, respectively (P<0.001). The corresponding figures in the keratoconus group were 492.0±61.7, 502.0±42.1, and 470.6±56.9 μm, respectively (P<0.001). Mean PCT was 612.5±35.3 and 640.9±38.0 μm in the normal group (P<0.001) and 567.6±35.2 and 595.1±41.4 μm in the keratoconus group (P<0.001) by the Galilei and Orbscan II, respectively. CCT and PCT measurements obtained by different devices were significantly correlated in both groups.
  
  
  CONCLUSIONS
  To measure CCT, the Galilei and Orbscan II can be used interchangeably in normal eyes, but not in keratoconic eyes. For PCT, there is a systematic error between measurements obtained by the Galilei and Orbscan II. However, it is possible to change optical pachymeter readings into those obtained by ultrasonic pachymetry using a constant.
authors: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Sepehr
authors: S
authors: Feizi
authors: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Mohammad Reza
authors: MR
authors: Jafarinasab
authors: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Farid
authors: F
authors: Karimian
authors: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Hosein
authors: H
authors: Hasanpour
authors: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Ali
authors: A
authors: Masudi
keywords: Central Corneal Thickness; Galilei; Keratoconus; Orbscan II; Peripheral Corneal Thickness; Ultrasonic Pachymetry