Purpose To study changes in anterior segment morphology after laser peripheral iridotomy (LPI) in primary angle closure (PAC) using anterior segment optical coherence tomography (AS-OCT). Methods LPI was performed on 15 consecutive primary angle closure patients (15 eyes). AS-OCT was used to record the morphology of the anterior segment before and after LPI. The central anterior chamber (AC) depth, the diameter of the pupil, the lens thickness, and the AC volume were measured. The peripheral AC depth and the configuration of iris were also observed qualitatively. The intraocular pressure (IOP) was measured by Goldmann applanation tonometer. Results The mean central AC depth was 1.939 +/- 0.228 and 1.970 +/- 0.235mm before and after LPI, respectively, increasing by 1.6%, P = 0.001. In all eyes but two, the central AC depth increased. The AC volume changed significantly after LPI (73.86 +/- 14.58 vs 84.14 +/- 17.45 mu l, P<0.001) and it increased in all eyes. The iris flattened and the peripheral AC deepened after LPI in all 15 eyes. The mean IOP was 17.8 +/- 3.3 and 15.9 +/- 3.1 mmHg before and after LPI, respectively, P = 0.042. The changes of pupil diameter and lens thickness were not statistically significant. Conclusions LPI leads not only to the increase of peripheral anterior chamber depth and anterior chamber volume but also to an increase of central anterior chamber depth in eyes with primary angle closure.