title: Comparison of central and peripheral corneal thickness measurements with scanning-slit, Scheimpflug and Fourier-domain ocular coherence tomography.
abstract: OBJECTIVE
  To compare central, regional and relational corneal thickness values obtained with multiple technologies in normal patients and to determine their equivalence and interchangeability.
  
  
  METHODS
  Retrospective analysis of 100 eyes from 50 patients evaluated by ultrasound pachymetry (Pachette II), scanning-slit (Orbscan II), Scheimpflug (Pentacam HR) and spectral-domain ocular coherence tomography (OCT) (RTVue-100) obtained as average values (OCT-A) and point measurements (OCT-P). Measurements included central corneal thickness (CCT) for all technologies and thinnest corneal thickness for scanning-slit, Scheimpflug and OCT. Peripheral thickness measurements were obtained at the 3 mm radius in the superior (S), nasal (N), inferior (I) and temporal (T) regions.
  
  
  RESULTS
  CCT values were: 563.9±36.1μ ultrasound, 570.9±36.1μ scanning-slit, 552.8±33.8μ Scheimpflug, 550.5±32.7μ (OCT-A), 549.4±32.7μ (OCT-P). Ultrasound and scanning-slit were significantly different from each other (p<0.0001), and both were significantly different from all other devices (p<0.0001), while Scheimpflug was similar to OCT-A and OCT-P (p=0.4). Differences between CCT and thinnest corneal thickness were significantly different from all technologies except scanning-slit and OCT-A. For peripheral values, almost all locations' measurements were significantly different from one another (p<0.0001). Superior-inferior values and ratios were also significantly different from one another for almost all devices with no consistent patterns detectible.
  
  
  CONCLUSIONS
  There are significant clinically relevant differences between regional and relational thickness measurements obtained with ultrasound, scanning-slit, Scheimpflug and OCT devices. Screening metrics devised for one system do not appear directly applicable to other measurement systems.
authors.affiliation: Department of Ophthalmology, Emory University, Atlanta, Georgia, USA Emory Vision, Emory Eye Center, Atlanta, Georgia, USA.
authors.forename: J Bradley
authors.initials: JB
authors.lastname: Randleman
authors.affiliation: Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lynn
authors.affiliation: Department of Ophthalmology, Emory University, Atlanta, Georgia, USA.
authors.forename: Claudia E
authors.initials: CE
authors.lastname: Perez-Straziota
authors.affiliation: Department of Ophthalmology, Emory University, Atlanta, Georgia, USA.
authors.forename: Heather M
authors.initials: HM
authors.lastname: Weissman
authors.affiliation: Department of Ophthalmology, University of Ulsan College of Medicine, Ulsan, South Korea.
authors.forename: Sang Woo
authors.initials: SW
authors.lastname: Kim
mesh_terms: D000328:Adult; D003315:Cornea / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D063171:Corneal Pachymetry / Q000379:methods*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010781:Photography / Q000295:instrumentation*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000295:instrumentation* / Q000379:methods; D014463:Ultrasonography; D055815:Young Adult
keywords: Cornea; Diagnostic tests/Investigation; Imaging; Treatment Lasers