title: Accuracy of Cirrus HD-OCT and Topcon SP-3000P for measuring central corneal thickness.
abstract: OBJECTIVE
  To compare and analyze the interchangeability of three measuring systems, each based on a different technique, for central corneal thickness (CCT) analysis.
  
  
  METHODS
  CCT measurements were measured using optical coherence tomography (OCT), non-contact specular microscopy (NCSM), and ultrasonic pachymetry (USP) in 60 eyes of 60 healthy patients with a mean age of 66.5±15.0 years and a mean spherical equivalent of 0.43±1.14 D. Analysis of variations in measurement concordance and correlation among the three different methods were performed. Comparison of CCT measurements were done using Bland-Altman plots (with bias and 95% confidence intervals), intraclass correlation coefficient (ICC), and paired t-student analysis.
  
  
  RESULTS
  Mean CCT values were: 549.20±26.91μm for USP (range 503-618μm), 514.20±27.49μm for NCSM (range 456-586μm) and 542.80±25.56μm for OCT (range 486-605μm). CCT values obtained with NCMS were significantly lower than those obtained with OCT and USP methods. NCMS CCT value was 36.08±10.72μm lower than USP value (p<0.05), and NCMS CCT value was 7.88±8.86μm lower than OCT value (p<0.05). ICC between USP-NCSM pair was 0.488 and 0.909 between USP-OCT pair.
  
  
  CONCLUSIONS
  OCT and UPS offered highly comparable results, whereas NCSM offered lower mean CCT values compared to the other two methods. Therefore, NCSM should not be considered a reliable method for measuring CCT and should rather be considered for assessing longitudinal changes in the same patient.
authors.affiliation: Instituto de Ciencias Visuales, Madrid, Spain. Electronic address: jacalvosanz@gmail.com.
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Calvo-Sanz
authors.affiliation: Universidad Europea, Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Ruiz-Alcocer
authors.affiliation: Universidad Europea, Madrid, Spain.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Sánchez-Tena
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D063171:Corneal Pachymetry / Q000295:instrumentation / Q000379:methods*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D008853:Microscopy / Q000379:methods*; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: Corneal pachymetry; Intercambiabilidad; Interchangeability; Microscopio especular; Optical coherence tomography; Paquimetría corneal; Paquimetría ultrasónica; Specular microscope; Tomografía de coherencia óptica; Ultrasound pachymetry