Objective  To describe new image analysis software for anterior chamber (AC) angle images obtained by the ultrasound biomicroscopy (UBM) and to assess its intraobserver and interobserver measurement reproducibility.

Methods  Images of right eyes of 30 patients with apparent narrow angles and right eyes of 30 patients with normal angles were consecutively chosen from a database. Each patient included 4 imags, which were superior, nasal, inferior and temporal quadrants of peripheral AC respectively. The angle parameters of the images, including angle opening distance (AOD), trabecular-iris angle (TIA), angle recess area (ARA), trabecular-ciliary process distance (TCPD), iris-ciliary process distance (ICPD), and iris thickness (IT) were measured and calculated twice by two observers used self-designed anterior angle analysis software. Intraobserver and interobserver reproducibility was evaluated by calculating an intraclass correlation coefficient (ICC). Bland-Altman plots were drawn as well.

Results  For intraobserver measurement, the ranges of ICC of AODs, TIAs, ARAs, TCPDs, ICPDs, and ITs in superior, nasal, inferior, and temporal quadrants of both narrow and normal angles were 0.83~0.94, 0.80~0.93, 0.82~0.94, 0.53~0.89, 0.42~0.84, and 0.70~0.95. For interobserver, the ranges of ICC of AODs, TIAs, ARAs, TCPDs, ICPDs, and ITs in all 4 quadrants of both narrow and normal angles were 0.56~0.89, 0.60~0.92, 0.64~0.92, 0.22~0.83, 0.48~0.93, and 0.28~0.75.

Conclusions  The parameters of angle width and iris thickness demonstrated reliable when measured by the same observer while the trabecular-ciliary process distance varied. We recommend measuring the anterior chamber parameters by the same observer.