title: Central corneal thickness measurements with optical coherence tomography and ultrasound pachymetry in healthy subjects and in patients after photorefractive keratectomy.
abstract: OBJECTIVE
  To compare central corneal thickness measurements made using two different methods, optical coherence tomography (OCT) and ultrasound pachymetry, applied both in normal eyes and in eyes on which photorefractive keratectomy (PRK) had been performed. A second objective was to assess the intrasession variability of OCT measurements.
  
  
  METHODS
  In this prospective study, central corneal thickness was measured in 20 normal subjects (normal group) and in 20 PRK patients using the StratusOCT instrument model 3000 (Carl Zeiss Meditec), and also with an ultrasound pachymeter. Five OCT measurements were performed using the Fast Macular Thickness protocol. Corneal thickness data were obtained with the Scan Profile analysis protocol. The OCT measurement results were compared with the mean value of three ultrasound pachymetry measurements for the same eye.
  
  
  RESULTS
  The pachymetry-OCT correlation coefficients were 0.96 and 0.97 in the normal and PRK groups, respectively (p=0.14). Neither linear regression nor Bland-Altmann analysis revealed any significant systematic measurement error. Intrasession standard deviations in the normal and PRK groups were 4.9 microm and 3.8 microm, respectively.
  
  
  CONCLUSIONS
  Noncontact central corneal thickness measurements made using the StratusOCT instrument are accurate and reproducible, both in normal subjects and in post-PRK patients. The instrument system does not need any modifications to correctly detect and measure the center of the cornea.
authors.affiliation: Department of Ophthalmology, Semmelweis University, Faculty of Medicine, Budapest - Hungary. schneider@szem1.sote.hu
authors.forename: Miklos
authors.initials: M
authors.lastname: Schneider
authors.forename: Gabor
authors.initials: G
authors.lastname: Borgulya
authors.forename: Andras
authors.initials: A
authors.lastname: Seres
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Nagy
authors.forename: Janos
authors.initials: J
authors.lastname: Nemeth
mesh_terms: D000328:Adult; D000368:Aged; D001837:Body Weights and Measures; D003315:Cornea / Q000033:anatomy & histology* / Q000473:pathology* / Q000601:surgery; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence; D014463:Ultrasonography; D055815:Young Adult