An ultrasound biomicroscopic dark-room provocative test.

Ultrasound biomicroscopy can image the relationship of angle structures under any lighting conditions. Eight patients with narrow angles were examined in the light and in the dark. All of the eyes showed iris thickening and shortening, increased anterior convexity of the iris, and varying degrees of angle narrowing in the dark. In one eye, the angle was completely closed. Iridotomy in this patient flattened the iris profile and opened the angle. The degree of angle opening observed after the iridotomy did not change depending on the lighting conditions. Ultrasound biomicroscopy allows imaging of dynamic changes in anterior ocular structures as they occur and provides information regarding angle occludability in the dark.