title: Comparison of techniques for measuring anterior chamber depth: Orbscan imaging, Smith's technique, and van Herick's method.
abstract: BACKGROUND
  Evaluation of anterior chamber depth (ACD) can potentially identify those patients at risk of angle-closure glaucoma. We aimed to: compare van Herick's limbal chamber depth (LCDvh) grades with LCDorb grades calculated from the Orbscan anterior chamber angle values; determine Smith's technique ACD and compare to Orbscan ACD; and calculate a constant for Smith's technique using Orbscan ACD.
  
  
  METHODS
  Eighty participants free from eye disease underwent LCDvh grading, Smith's technique ACD, and Orbscan anterior chamber angle and ACD measurement.
  
  
  RESULTS
  LCDvh overestimated grades by a mean of 0.25 (coefficient of repeatability [CR] 1.59) compared to LCDorb. Smith's technique (constant 1.40 and 1.31) overestimated ACD by a mean of 0.33 mm (CR 0.82) and 0.12 mm (CR 0.79) respectively, compared to Orbscan. Using linear regression, we determined a constant of 1.22 for Smith's slit-length method.
  
  
  CONCLUSIONS
  Smith's technique (constant 1.31) provided an ACD that is closer to that found with Orbscan compared to a constant of 1.40 or LCDvh. Our findings also suggest that Smith's technique would produce values closer to that obtained with Orbscan by using a constant of 1.22.
authors.affiliation: Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK. f.eperjesi@aston.ac.uk
authors.forename: Frank
authors.initials: F
authors.lastname: Eperjesi
authors.forename: Claire
authors.initials: C
authors.lastname: Holden
mesh_terms: D000293:Adolescent; D000328:Adult; D000867:Anterior Chamber / Q000473:pathology*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D055815:Young Adult