Purpose: To demonstrate appositional angle closure using ultrasound biomicroscopy under dark room conditions, to investigate patterns of appositional closure, and to correlate those patterns with the angle topology in eyes with narrow angles.
Methods: Forty-six eyes that met the study criteria, from 46 individuals, were examined by ultrasound biomicroscopy under dark room and illuminated conditions.
Results: In 40 of the 46 eyes (87.0%), appositional closure was identified by ultrasound biomicroscopy. Two distinct patterns of angle closure were seen: type B, in which closure starts from the bottom of the angle, and type S, in which closure starts in the vicinity of Schwalbe's line. In type B, the iris root was located closure to the chamber angle than in type S.
Conclusions: Ultrasound biomicroscopy performed under dark room conditions is a useful technique for identifying appositional angle closure in eyes with narrow angles. The topology of the iris root is related to the pattern of the appositional angle closure.