title: A proposed simple method for measurement in the anterior chamber angle: biometric gonioscopy.
abstract: OBJECTIVE
  To design a system of gonioscopy that will allow greater interobserver reliability and more clearly defined screening cutoffs for angle closure than current systems while being simple to teach and technologically appropriate for use in rural Asia, where the prevalence of angle-closure glaucoma is highest.
  
  
  METHODS
  Clinic-based validation and interobserver reliability trial.
  
  
  METHODS
  Study 1: 21 patients 18 years of age and older recruited from a university-based specialty glaucoma clinic; study 2: 32 patients 18 years of age and older recruited from the same clinic.
  
  
  METHODS
  In study 1, all participants underwent conventional gonioscopy by an experienced observer (GLS) using the Spaeth system and in the same eye also underwent Scheimpflug photography, ultrasonographic measurement of anterior chamber depth and axial length, automatic refraction, and biometric gonioscopy with measurement of the distance from iris insertion to Schwalbe's line using a reticule based in the slit-lamp ocular. In study 2, all participants underwent both conventional gonioscopy and biometric gonioscopy by an experienced gonioscopist (NGC) and a medical student with no previous training in gonioscopy (JK).
  
  
  METHODS
  Study 1: The association between biometric gonioscopy and conventional gonioscopy, Scheimpflug photography, and other factors known to correlate with the configuration of the angle. Study 2: Interobserver agreement using biometric gonioscopy compared to that obtained with conventional gonioscopy.
  
  
  RESULTS
  In study 1, there was an independent, monotonic, statistically significant relationship between biometric gonioscopy and both Spaeth angle (P = 0.001, t test) and Spaeth insertion (P = 0.008, t test) grades. Biometric gonioscopy correctly identified six of six patients with occludable angles according to Spaeth criteria. Biometric gonioscopic grade was also significantly associated with the anterior chamber angle as measured by Scheimpflug photography (P = 0.005, t test). In study 2, the intraclass correlation coefficient between graders for biometric gonioscopy (0.97) was higher than for Spaeth angle grade (0.72) or Spaeth insertion grade (0.84).
  
  
  CONCLUSIONS
  Biometric gonioscopy correlates well with other measures of the anterior chamber angle, shows a higher degree of interobserver reliability than conventional gonioscopy, and can readily be learned by an inexperienced observer.
authors.affiliation: William and Anna Goldberg Glaucoma Service, Wills Eye Hospital, Philadelphia, Pennsylvania, USA.
authors.forename: N G
authors.initials: NG
authors.lastname: Congdon
authors.forename: G L
authors.initials: GL
authors.lastname: Spaeth
authors.forename: J
authors.initials: J
authors.lastname: Augsburger
authors.forename: J
authors.initials: J
authors.lastname: Klancnik
authors.forename: K
authors.initials: K
authors.lastname: Patel
authors.forename: D G
authors.initials: DG
authors.lastname: Hunter
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000867:Anterior Chamber / Q000000981:diagnostic imaging / Q000473:pathology*; D001699:Biometry; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis*; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006068:Gonioscopy / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010781:Photography; D015203:Reproducibility of Results; D014463:Ultrasonography