title: Precision of high definition spectral-domain optical coherence tomography for measuring central corneal thickness.
abstract: OBJECTIVE
  This study was intended to assess the reliability of central corneal thickness (CCT) measurements using Cirrus high-definition optical coherence tomography (HD-OCT) in healthy subjects and its accuracy compared with ultrasonic pachymetry.
  
  
  METHODS
  Seventy-seven consecutive subjects were recruited for evaluating repeatability, and agreement between two examiners. To analyze repeatability, one examiner measured 77 eyes four times in succession. To study agreement between two observers, a second independently trained examiner obtained another CCT measurement. We also measured eyes in a subgroup of 20 patients using standard ultrasonic pachymetry. Within-subject standard deviation (S(w)), coefficient of variation (CV), limits of agreement (LoA), and intraclass correlation coefficient (ICC) data were obtained.
  
  
  RESULTS
  For repeatability, the S(w) and precision (1.96 × S(w)) were 4.86 and 9.52 μm, respectively. Intraobserver CV was 0.89% and the ICC was 0.98 (95% confidence interval [CI], 0.97-0.99). For agreement between two examiners, the S(w) and precision were 7.58 and 14.85 μm, respectively; the CV was 1.40%. The mean difference between observers was -0.13 μm (95% CI, -1.85 to 1.58; P = 0.87). The width of the LoA was 29.64 μm. Median difference between Cirrus HD-OCT and ultrasound CCT measurements was -4.5 μm (interquartile range, -7.0-0.0; P = 0.04).
  
  
  CONCLUSIONS
  Cirrus HD-OCT provides repeatable CCT measurements, good agreement between two independently trained examiners, and its systematic bias compared to ultrasonic pachymetry is clinically negligible. Therefore, research laboratories and eye clinics using Cirrus HD-OCT as a diagnostic imaging method, can also benefit from a reliable noncontact pachymeter when counseling patients with glaucoma and those undergoing corneal and refractive surgeries.
authors.affiliation: Rio Hortega University Hospital, Valladolid, Spain.
authors.forename: María E
authors.initials: ME
authors.lastname: Correa-Pérez
authors.forename: Alberto
authors.initials: A
authors.lastname: López-Miguel
authors.forename: Silvia
authors.initials: S
authors.lastname: Miranda-Anta
authors.forename: Darío
authors.initials: D
authors.lastname: Iglesias-Cortiñas
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Alió
authors.forename: Miguel J
authors.initials: MJ
authors.lastname: Maldonado
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology*; D003316:Corneal Diseases / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence / Q000379:methods*; D014463:Ultrasonography; D055815:Young Adult