title: Comparison of central corneal thickness measurements by rotating Scheimpflug camera, ultrasonic pachymetry, and scanning-slit corneal topography.
abstract: OBJECTIVE
  To compare central corneal thickness measurements and their reproducibility when taken by a rotating Scheimpflug camera, ultrasonic pachymetry, and scanning-slit corneal topography/pachymetry.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Seventy-four eyes of 64 subjects without ocular abnormalities other than cataract.
  
  
  METHODS
  Corneal thickness measurements were compared among the 3 methods in 54 eyes of 54 subjects. Two sets of measurements were repeated by a single examiner for each pachymetry in another 10 eyes of 5 subjects, and the intraexaminer repeatability was assessed as the absolute difference of the first and second measurements. Two experienced examiners took one measurement for each pachymetry in another 10 eyes of 5 subjects, and the interexaminer reproducibility was assessed as the absolute difference of the 2 measurements of the first and second examiners.
  
  
  METHODS
  Central corneal thickness measurements by the 3 methods, absolute difference of the first and second measurements by a single examiner, absolute difference of the 2 measurements by 2 examiners, and relative amount of variation.
  
  
  RESULTS
  The average measurements of central corneal thickness by a rotating Scheimpflug camera, scanning-slit topography, and ultrasonic pachymetry were 538+/-31.3 microm, 541+/-40.7 microm, and 545+/-31.3 microm, respectively. There were no statistically significant differences in the measurement results among the 3 methods (P = 0.569, repeated-measures analysis of variance). There was a significant linear correlation between the rotating Scheimpflug camera and ultrasonic pachymetry (r = 0.908, P<0.0001), rotating Scheimpflug camera and scanning-slit topography (r = 0.930, P<0.0001), and ultrasonic pachymetry and scanning-slit topography (r = 0.887, P<0.0001). Ultrasonic pachymetry had the smallest intraexaminer variability, and scanning-slit topography had the largest intraexaminer variability among the 3 methods. There were similar variations in interexaminer reproducibility among the 3 methods.
  
  
  CONCLUSIONS
  Mean corneal thicknesses were comparable among rotating Scheimpflug camera, ultrasonic pachymetry, and scanning-slit topography with the acoustic equivalent correction factor. The measurements of the 3 instruments had significant linear correlations with one another, and all methods had highly satisfactory measurement repeatability.
authors.affiliation: Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan. amanos-tky@umin.ac.jp
authors.forename: Shiro
authors.initials: S
authors.lastname: Amano
authors.forename: Norihiko
authors.initials: N
authors.lastname: Honda
authors.forename: Yuki
authors.initials: Y
authors.lastname: Amano
authors.forename: Satoru
authors.initials: S
authors.lastname: Yamagami
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyai
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Samejima
authors.forename: Miyuki
authors.initials: M
authors.lastname: Ogata
authors.forename: Kazunori
authors.initials: K
authors.lastname: Miyata
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001837:Body Weights and Measures; D002386:Cataract / Q000150:complications; D003315:Cornea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D019781:Corneal Topography; D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010781:Photography; D011446:Prospective Studies; D015203:Reproducibility of Results; D014463:Ultrasonography