Background/Aims: To determine whether the volume of the posterior chamber changes during pupillary dilation.
Methods: Eyes with anatomically narrow angles underwent ultrasound biomicroscopy of the posterior chamber and pupillary margin under dark and light room conditions to assess changes in posterior chamber anatomy and volume. All examinations were stored as real-time video. Frame-by-frame analysis was performed using a macro written for the ImageJ image-processing software.
Results: Thirteen eyes were assessed. Mean patient age was 63.0 ± 10.0 (S.D.) years and mean refractive error was 1.1 ± 1.9 diopters. Horizontal mean pupillary diameter was 2.3 ± 0.6 mm and 3.5 ± 0.5 mm under light and dark room conditions, respectively (p < 10-7, paired t-test). Mean posterior chamber volumes were unchanged under light and dark conditions (3.76 ± 1.09 vs. 3.63 ± 0.78 mm3, p=0.22, paired t-test). Volumes were greater under light conditions in 8 eyes and under dark conditions in 5 eyes.