Assessment of Circumferential Angle-Closure by the Iris–Trabecular Contact Index with Swept-Source Optical Coherence Tomography

• Published in: Ophthalmology (Rochester, Minn.) Vol. 120; no. 11; pp. 2226 - 2231
• Main Authors: Baskaran, Mani, Ho, Sue-Wei, Tun, Tin A., How, Alicia C., Perera, Shamira A., Friedman, David S., Aung, Tin
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2013
• Subjects: Anterior Chamber - pathology; Area Under Curve; Female; Glaucoma, Angle-Closure - diagnosis; Gonioscopy; Humans; Imaging, Three-Dimensional; Intraocular Pressure; Iris - pathology; Male; Middle Aged; Ophthalmology; Prospective Studies; Tissue Adhesions; Tomography, Optical Coherence - methods; Tonometry, Ocular; Trabecular Meshwork - pathology
• ISSN: 0161-6420; 1549-4713; 1549-4713
• DOI: 10.1016/j.ophtha.2013.04.020

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. Prospective observational study. A total of 108 normal subjects and 32 subjects with angle-closure. 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. 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. 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%. 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. The author(s) have no proprietary or commercial interest in any materials discussed in this article.