title: Corneal diameter measurements by corneal topography and angle-to-angle measurements by optical coherence tomography: evaluation of equivalence.
abstract: OBJECTIVE
  To determine the equivalence of corneal white-to-white (WTW) diameter and anterior segment angle-to-angle (ATA) measurements.
  
  
  METHODS
  Vissum Instituto Oftalmologico de Alicante, Alicante, Spain.
  
  
  METHODS
  Thirty eyes of 19 patients ranging in age from 20 to 51 years old with no previous ocular surgeries were included in this study. In all cases, the horizontal WTW diameter was measured with a tool provided by the CSO corneal topography system (Costruzione Strumenti Oftalmici) and the horizontal ATA was measured using an optical coherence tomography (OCT) system (Visante, Carl Zeiss Meditec AG). All measurements were repeated 3 times to evaluate intrasession repeatability. The correlation between WTW and ATA measurements was studied, and the interchangeability of the 2 parameters was assessed using the Bland and Altman method.
  
  
  RESULTS
  The mean corneal WTW diameter was 12.25 mm +/- 0.49 (SD) (range 11.34 to 13.16 mm), and the mean ATA distance was 11.76 +/- 0.52 mm (range 10.03 to 12.92 mm). The difference between the 2 parameters was statistically significant (P<.01). A weak, although statistically significant, positive correlation (r = 0.39; P = .03) and a nonpredictive linear model were found. The Bland and Altman analysis showed large limits of agreement between WTW and ATA measurements that are clinically relevant (limits of agreement, -1.59 mm and 0.61 mm). The intrasession repeatability scores for the WTW and ATA measurements were good.
  
  
  CONCLUSIONS
  The WTW and ATA distance measurements were not equivalent and thus are not interchangeable. There was no linear model for an accurate prediction of the ATA from the WTW.
authors.affiliation: Vissum/Instituto Oftalmológico de Alicante, Universidad Miguel Hernández, Alicante, Spain.
authors.forename: David P
authors.initials: DP
authors.lastname: Piñero
authors.forename: Ana Belén
authors.initials: AB
authors.lastname: Plaza Puche
authors.forename: Jorge L
authors.initials: JL
authors.lastname: Alió
mesh_terms: D000328:Adult; D001699:Biometry; D001837:Body Weights and Measures; D003315:Cornea / Q000033:anatomy & histology*; D019781:Corneal Topography / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000379:methods*