Comparison of ultrasound biomicroscopic parameters after laser iridotomy in eyes with primary angle closure and primary angle closure glaucoma

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.