title: Reliability and validity of the partial coherence interferometry for measurement of ocular axial length in children.
abstract: OBJECTIVE
  To assess the validity and repeatability of partial coherence interferometry (IOLMaster) and A-scan ultrasound measurement of axial length (AL) in children.
  
  
  METHODS
  A prospective comparison of AL measurement made by the IOLMaster optical instrument (Carl Zeiss) and ultrasound A-scan (Alcon) was performed. A total of 20 children (11 male, nine female) were recruited into the study; the mean age of the sample was 11.4 years (range 6.2-15.8). Inclusion criteria comprised individuals <16 years, with no ocular pathology and no previous eye operations or allergy to topical anaesthetics. All measurements were performed by a single examiner.
  
  
  RESULTS
  Data on validity show that, on average, a small measurement difference existed between these groups with the IOLMaster being 0.017 mm greater than A-scan ultrasonography. The 95% confidence interval for this difference encompasses zero, demonstrating that no significant systematic bias exists between the two-measurement techniques. Overall, IOLMaster reliability exceeded that of A-scan. This is evidenced primarily by the spread of the paired test-retest difference for A-scan compared to IOLMaster. The mean test-retest difference for A-scan was considerably larger than IOLMaster at 0.042 and 0.004 mm, respectively.
  
  
  CONCLUSIONS
  The results show that IOLMaster was more accurate and reproducible than the contact ultrasonographic technique when used in children. Such results indicate that IOLMaster may be a useful tool in studies of eye growth and refractive development in children.
authors.affiliation: Bristol Eye Hospital, Bristol, UK.
authors.forename: H M
authors.initials: HM
authors.lastname: Hussin
authors.forename: P G D
authors.initials: PG
authors.lastname: Spry
authors.forename: M A
authors.initials: MA
authors.lastname: Majid
authors.forename: P
authors.initials: P
authors.lastname: Gouws
mesh_terms: D000293:Adolescent; D001699:Biometry / Q000379:methods; D002648:Child; D003941:Diagnostic Techniques, Ophthalmological; D005123:Eye / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007368:Interferometry / Q000379:methods; D008297:Male; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D014463:Ultrasonography