title: Anterior chamber depth measurement with a-scan ultrasonography, Orbscan II, and IOLMaster.
abstract: OBJECTIVE
  The authors conducted a comparison of anterior chamber depth (ACD) measurement by 3 devices of EchoScan, Orbscan II, and IOLMaster to assess the validity of the latter 2 and its reliability with Orbscan II.
  
  
  METHODS
  Forty-four myopic patients, 56.8% female, were enrolled in this prospective study. In all 88 eyes, the ACD was first measured with Orbscan II, followed by IOLMaster and EchoScan U3300, both under cycloplegia. The mean (+/-standard deviation) age and spherical equivalent were 30.2+/-8.5 years and -4.98+/-2.67 D, respectively. The difference between ACD measurements by these 3 devices was analyzed using the repeated-measures analysis of variance. Agreement between each pair of devices was assessed by computing the 95% limits of agreement (LoA). Orbscan II reliability was also evaluated by using the 95% LoA between 2 consecutive measurements. P value adjustments for multiple comparisons were performed using the Bonferroni method.
  
  
  RESULTS
  There was a statistically significant difference between measurements made with the 3 devices (p<0.001). The mean difference between Orbscan II and Echoscan ACD measurements was -0.03+/-0.12 mm, with the 95% LoA from -0.25 to +0.20 mm, and between IOLMaster and Echoscan measurements, it was +0.09+/-0.14 mm with the 95% LoA from -0.18 to +0.36 mm. On average, Orbscan II readings were lower and those of IOLMaster were higher than Echoscan readings. Both Orbscan II and IOLMaster agreed with Echoscan in measuring ACD. The 2 readings by Orbscan II had a 95% LoA of -0.05 and +0.07 mm that shows good reliability.
  
  
  CONCLUSIONS
  ACD measurement differences with the 3 studied devices proved to be statistically significant; however, these minor differences may be clinically negligible depending on the use of the measurement. As an advantage, both Orbscan II and IOLMaster are noncontact, and with their ACD measurements being valid, they may be considered suitable devices for this purpose. In addition, Orbscan II produces highly repeatable ACD measurements.
authors.affiliation: Farabi Eye Hospital, Department of Ophthalmology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
authors.forename: Kamran
authors.initials: K
authors.lastname: Yazdani
authors.forename: Shiva
authors.initials: S
authors.lastname: Mehravaran
authors.forename: Akbar
authors.initials: A
authors.lastname: Fotouhi
mesh_terms: D000328:Adult; D000867:Anterior Chamber / Q000000981:diagnostic imaging* / Q000473:pathology*; D003936:Diagnosis, Computer-Assisted / Q000592:standards; D005260:Female; D006801:Humans; D007368:Interferometry / Q000592:standards; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000175:diagnosis* / Q000000981:diagnostic imaging; D015203:Reproducibility of Results; D014463:Ultrasonography