title: Technical note: Accuracy and repeatability of a new portable ultrasound pachymeter.
abstract: OBJECTIVE
  To assess the accuracy and repeatability of central corneal thickness (CCT) measurements taken with a new portable ultrasound (US) pachymeter.
  
  
  METHODS
  Central thickness measurements were taken with a portable pachymeter (SP-100 Handy; Tomey, Nagoya, Japan) and a conventional US pachymeter (Nidek UP-1000; Nidek Technologies, Gamagori, Japan) from 57 right corneas of 57 young adults (19 males, 38 females) aged 18-44 years (mean +/- S.D., 22.95 +/- 3.92). Three repeated measures were obtained and then compared to obtain the repeatability of each instrument and the agreement between the pachymeters. The three readings taken with the portable pachymeter were compared against each other in order to evaluate intra-session repeatability and bias of each individual measurement with respect to the mean of three.
  
  
  RESULTS
  Mean values of CCT were 537 +/- 35 microm for conventional and 534 +/- 35 microm for the new portable pachymeter. A high agreement was found between the two instruments (mean difference = 2.58 microm; 95% CI 1.41-3.75 microm) with only two eyes presenting differences larger than +/-8.6 microm which represents 95% CI in the Bland-Altman plots which represents 1.6% of the mean CCT. The first reading taken showed the highest agreement with the mean value for the portable pachymeter.
  
  
  CONCLUSIONS
  The instrument tested in this study is able to take reliable measurements of corneal thickness even if a single reading is considered. Intra-session repeatability was very high, as was also the agreement between the average of three readings taken with the two US pachymeters.
authors.affiliation: Department of Physics (Optometry), School of Sciences, Campus de Gualtar, University of Minho, 4710-057 Braga, Portugal. aqp@fisica.uminho.pt
authors.forename: A
authors.initials: A
authors.lastname: Queirós
authors.forename: J M
authors.initials: JM
authors.lastname: González-Méijome
authors.forename: P
authors.initials: P
authors.lastname: Fernandes
authors.forename: J
authors.initials: J
authors.lastname: Jorge
authors.forename: J B
authors.initials: JB
authors.lastname: Almeida
authors.forename: M A
authors.initials: MA
authors.lastname: Parafita
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000000981:diagnostic imaging*; D019781:Corneal Topography / Q000295:instrumentation*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D014463:Ultrasonography