Dynamic changes in anterior segment morphology during the Valsalva maneuver assessed with ultrasound Biomicroscopy

We evaluated dynamic changes in anterior segment morphology during the Valsalva maneuver with ultrasound biomicroscopy (UBM). For this prospective observational study, a group of patients with narrow angles and a group of normal subjects were recruited. The anterior segment of subjects was imaged and analyzed quantitatively using UBM before and during the Valsalva maneuver. Changes in anterior segment parameters from baseline and during the Valsalva maneuver, and the differences in parameters between the narrow angle and control groups were analyzed. Of 151 subjects recruited for the study, 68 (45.0%) were men and 83 (54.9%) had narrow angles. For the overall group, during Valsalva maneuver, the subjects' central anterior chamber depth (ACD) became shallower (from 2.286-2.262 mm, P < 0.001), and the anterior chamber angle became narrower (from 14.673-13.370 degrees, P = 0.004), the angle opening distance became smaller (from 0.158-0.140 mm, P = 0.014), and the peripheral iris thickness became thicker (from 0.494-0.508 mm, P = 0.041), while the central iris thickness did not change. Compared to normal controls, narrow angle subjects had shallower ACD and thicker iris at baseline, but there was no significant difference between the 2 groups in dynamic changes in the anterior segment after the Valsalva maneuver. The Valsalva maneuver, performed frequently in daily activities, can lead to significant narrowing of the angles in subjects with open and narrow angles. This factor may be important in eyes at risk for angle closure glaucoma.