title: Comparison of lens thickness measurements using the anterior segment optical coherence tomography and A-scan ultrasonography.
abstract: OBJECTIVE
  To assess lens thickness (LT) measurements with anterior segment optical coherence tomography (AS-OCT) in comparison with A-scan ultrasonography (A-scan US).
  
  
  METHODS
  Enrolled were 66 eyes of 48 phakic elderly volunteers aged > or = 50 years and 56 eyes of 56 young participants aged 18 to 40 years. LT was measured with the internal manual caliper tools in AS-OCT. The A-scan US measurements were based on an average of 10 consecutive automatic measurements. Reproducibility was assessed by three measurements each with AS-OCT and A-scan US independently obtained by two observers who were masked to one another's results.
  
  
  RESULTS
  The failure rates of AS-OCT and A-scan US were 9.1% and 7.6%, respectively, in elderly subjects, but no failure was observed in young subjects. The LT values measured by AS-OCT were significantly greater than A-scan US; the paired difference was 0.135 mm in elderly and 0.101 mm in young subjects (P < 0.001). These differences did not correlate with the nuclear cataract grades (r = 0.078, P = 0.558). Intraobserver agreement on AS-OCT (95% limits of agreement [LoA]: -0.049 to +0.045 mm; ICC: 0.999) was better than A-scan US (95%LoA: -0.194 to +0.218 mm; ICC: 0.974). The 95% LoA of interobserver agreement using AS-OCT and A-scan were -0.084 to +0.073 and -0.278 to +0.239 mm, respectively, and the ICCs were 0.996 and 0.960, respectively.
  
  
  CONCLUSIONS
  AS-OCT can be used to measure lens thickness in most eyes with clear or opacified lenses. It appears to be an alternative means of measuring lens thickness, particularly when a noncontact method is needed.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Yangfa
authors.initials: Y
authors.lastname: Zeng
authors.forename: Yizhi
authors.initials: Y
authors.lastname: Liu
authors.forename: Xing
authors.initials: X
authors.lastname: Liu
authors.forename: Chuying
authors.initials: C
authors.lastname: Chen
authors.forename: Yuanling
authors.initials: Y
authors.lastname: Xia
authors.forename: Miaoling
authors.initials: M
authors.lastname: Lu
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001699:Biometry; D002386:Cataract / Q000175:diagnosis* / Q000000981:diagnostic imaging; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods; D014463:Ultrasonography / Q000379:methods; D055815:Young Adult