title: The repeatability and accuracy of axial length and anterior chamber depth measurements from the IOLMaster .
abstract: BACKGROUND
  Axial length and anterior chamber depth have been measured clinically using conventional ultrasound biometry. Recently, a non-contact device has become available to measure these parameters. This study evaluated the repeatability and accuracy of this device.
  
  
  METHODS
  The axial length and anterior chamber depth were measured by two practitioners on a group of young subjects using the IOLMaster followed by a conventional ultrasound biometer operated by a third practitioner. The accommodation was controlled in ultrasound biometry through a full correction on the non-measured eye and a distant fixation target.
  
  
  RESULTS
  There was good repeatability and accuracy of axial length assessment. The mean difference between the IOLMaster and ultrasound biometry was -0.099 mm, with 95% limits of agreement between 0.66 and -0.85 mm. The axial length was slightly shorter from the IOLMaster and the difference was not significant. The anterior chamber depth was repeatable but was shown to be deeper than the ultrasound results. The mean difference in anterior chamber depth between the IOLMaster and ultrasound biometry was 0.15 mm, with 95% limits of agreement between 0.34 and -0.03 mm. It is suggested that the former device is not measuring the axial anterior chamber depth.
  
  
  CONCLUSIONS
  The IOLMaster is a non-contact 'optical' A-scan which is simple to use and good for axial length assessment. The anterior chamber depth assessment should be further evaluated.
authors.affiliation: Department of Optometry and Radiography, The Hong Kong Polytechnic University, Kowloon. orkclam@polyu.edu.hk
authors.forename: A K
authors.initials: AK
authors.lastname: Lam
authors.forename: R
authors.initials: R
authors.lastname: Chan
authors.forename: P C
authors.initials: PC
authors.lastname: Pang
mesh_terms: D000328:Adult; D000867:Anterior Chamber / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D001699:Biometry / Q000295:instrumentation*; D005123:Eye / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D006801:Humans; D007368:Interferometry / Q000295:instrumentation; D008027:Light; D016011:Normal Distribution; D015203:Reproducibility of Results; D018709:Statistics, Nonparametric; D014463:Ultrasonography