Assessment of circumferential angle-closure by the iris-trabecular contact index with swept-source optical coherence tomography

Ophthalmology. 2013 Nov;120(11):2226-31. doi: 10.1016/j.ophtha.2013.04.020. Epub 2013 Jun 14.


Purpose: To evaluate the diagnostic performance of the iris-trabecular contact (ITC) index, a measure of the degree of angle-closure, using swept-source optical coherence tomography (SSOCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan) in comparison with gonioscopy.

Design: Prospective observational study.

Participants: A total of 108 normal subjects and 32 subjects with angle-closure.

Methods: The SSOCT 3-dimensional angle scans, which obtain radial scans for the entire circumference of the angle, were performed under dark conditions and analyzed using customized software by a single examiner masked to the subjects' clinical details. The ITC index was calculated as a percentage of the angle that was closed on SSOCT images. First-order agreement coefficient (AC1) statistics and area under the receiver operating characteristic curve (AUC) analyses were performed for angle-closure on the basis of the ITC index in comparison with gonioscopy.

Main outcome measures: Angle-closure on gonioscopy was defined as nonvisibility of posterior trabecular meshwork for at least 2 quadrants. Agreement of the ITC index with gonioscopically defined angle-closure was assessed using the AC1 statistic.

Results: Study subjects were predominantly Chinese (95.7%) and female (70.7%), with a mean age of 59.2 (standard deviation, 8.9) years. The median ITC index was 15.24% for gonioscopically open-angle eyes (n = 108) and 48.5% for closed-angle eyes (n = 32) (P = 0.0001). The agreement for angle-closure based on ITC index cutoffs (>35% and ≥50%) and gonioscopic angle-closure was 0.699 and 0.718, respectively. The AUC for angle-closure detection using the ITC index was 0.83 (95% confidence interval, 0.76-0.89), with an ITC index >35% having a sensitivity of 71.9% and specificity of 84.3%.

Conclusions: The ITC index is a summary measure of the circumferential extent of angle-closure as imaged with SSOCT. The index had moderate agreement and good diagnostic performance for angle-closure with gonioscopy as the reference standard.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anterior Chamber / pathology
  • Area Under Curve
  • Female
  • Glaucoma, Angle-Closure / diagnosis*
  • Gonioscopy
  • Humans
  • Imaging, Three-Dimensional
  • Intraocular Pressure
  • Iris / pathology*
  • Male
  • Middle Aged
  • Prospective Studies
  • Tissue Adhesions
  • Tomography, Optical Coherence / methods*
  • Tonometry, Ocular
  • Trabecular Meshwork / pathology*