Diagnostic Disagreement Between Gonioscopy and Ultrasound Biomicroscopy in Eyes With Occludable Angle

PRÉCIS: Disagreement in the angle closure assessment was seen between gonioscopy and ultrasound biomicroscopy (UBM), to which not only anterior, but also posterior chamber configuration UBM parameters were significantly related. PURPOSE: To study diagnostic disagreement and its relating factors in assessing the angle classified as "occludable" by gonioscopy and by ultrasound biomicroscopy in eyes with van Herick grade 2 or less (eyes ≤VH2). METHODS: In 93 eyes ≤VH2 (93 subjects) with no peripheral anterior synechia, gonioscopy, UBM, and anterior segment-optical coherence tomography (AS-OCT) were performed in dark, the number of eyes with ≥2 ITC-positive quadrants (contact ≥180 degrees) based on UBM (eyes ≥2-ITC UBM Quad) and that with the angle classified as occludable by gonioscopy (eyes≥2-ITC GONIO Quad) were determined, and the number of eyes not meeting these criteria, that is, eyes <2-ITC UBM Quad (contact <180 degrees) and eyes <2-ITC GONIO Quad, was also determined. Multivariable logistic regression analysis was performed with systemic, ocular, UBM, and AS-OCT parameters as explanatory variables. RESULTS: Out of the 93 eyes, 49 were diagnosed as eyes ≥2-ITC GONIO Quad based on gonioscopy, 63 as eyes ≥2-ITC UBM Quad on UBM, 37 as both eyes ≥2-ITC GONIO Quad and eyes ≥2-ITC UBM Quad (agreement between gonioscopy and UBM), 12 as eyes ≥2-ITC GONIO Quad base on gonioscopy, but as eyes <2-ITC UBM Quad on UBM (UBM under-diagnosing), and 26 as eyes <2-ITC GONIO Quad based on gonioscopy, but as eyes ≥2-ITC UBM Quad on UBM (UBM over-diagnosing), respectively (McNemar test, P =0.0388). Longer axial length ( P =0.0002), deeper anterior chamber depth ( P =0.0121), greater angle-opening distance at 500 μm ( P =0.0159), and smaller iris convexity ( P =0.0031) were related to UBM over-diagnosing, while a greater angle-opening distance at 500 μm ( P =0.0046) and smaller trabecular ciliary angle ( P =0.0158) to UBM under-diagnosing. CONCLUSION: Both anterior and posterior chamber configuration parameters determined based on UBM were significantly related to disagreement between gonioscopy and UBM in assessing the appositional angle closure.