Objective To assess the agreement between gonioscopy and ultrasound biomicroscopy (UBM) in detecting angle closure in Chinese patients with shallow anterior chamber. Methods An observational comparative study of the two different examination methods was conducted. Patients with normal intraocular pressure and temporal peripheral anterior chamber depth less than a quarter of corneal thickness based on slit lamp examination were included in this study from December 2007 to May 2009 in the outpatient clinic of First Hospital of Tsinghua University. Gonioscopy was performed with a Goldman goniolens in dark room first and followed by full beam light and indentation. If the filtering trabecular meshwork was invisible or any peripheral anterior synechia was found

that quadrant of the angle was considered closed. UBM was first undertaken in a darkened room then repeated with normal room lighting. If iridotrabecular apposition was showed

that quadrant of the angle was considered closed. The status of angle closure of each quadrant with different methods was recorded. Results 85 eyes of 46 patients were included in this study. The agreement between gonioscopy and UBM was poor (κ<0.4) with Kappa analysis in both dark and light conditions in each quadrant. The accordance of agreement between gonioscopy and UBM was hardly affected by age or sex

while in dark condition

eyes with deeper anterior chamber (P=0.005) or plateau iris configuration tended to produce different results (P=0.075) in the 2 methods. Conclusion Gonioscopy and UBM are both indispensable methods for detecting angle closure

neither can completely replace the other.