Purpose: To study changes in anterior segment morphology after laser peripheral iridotomy (LPI) in primary angle closure (PAC) and primary angle closure glaucoma (PACG) using ultrasound biomicroscopy (UBM).
Methods: Ninety-three eyes of 93 patients underwent anterior segment evaluation including gonioscopy, disc evaluation with + 90D lens, applanation intraocular pressure, and standard achromatic perimetry. UBM was performed before and 2 weeks after Nd:YAG LPI to measure the trabecular-iris angle (TIA), the angle-opening distance (AOD 250/500), and the central anterior chamber depth (ACD).
Results: The superior TIA widened from a mean of 7.54+/-3.15 to 15.66+/-6.69 degrees (P=0.0001), the inferior TIA increased from a mean of 9.0+/-4.7 to 15.9+/-6.8 degrees (P=0.0001) after LPI in PAC. In PACG, the mean superior angle changed from 4.55+/-2.5 to 6.12+/-3.8 degrees (P=0.4) and the inferior angle increased from 4.75+/-2.0 to 7.9+/-3.7 degrees (P=0.1). The mean ACD increased from 2.19+/-0.36 to 2.30+/-0.36 mm in PAC group (P=0.0003), with no significant change seen in the PACG group (1.79+/-0.32 vs 1.82+/-0.33 mm, P=0.13).
Conclusion: LPI leads to a widening of the anterior chamber angle and a deepening of the anterior chamber in eyes with PAC. It does not significantly change any anterior segment parameters in eyes with PACG.