Assessment of the changes in anterior segment parameters by ultrasound biomicroscopy after laser peripheral iridotomy

Purpose The aim of this study was to evaluate the changes in anterior segment parameters by ultrasound biomicroscopy (UBM) after laser peripheral iridotomy (LPI) in eyes with narrow drainage angles.Patients and methods A prospective study was conducted on 20 eyes of 20 different patients with primary angle-closure glaucoma in need for LPI. Patients underwent a detailed ophthalmic examination including slit lamp examination, intraocular pressure measurement, and gonioscopy. UBM was performed before and 1 week after LPI. Quantitative parameters included angle-opening distance (AOD), iris thickness, trabecular-iris angle, trabecular-ciliary process distance, iris-lens contact distance (ILCD), and iridocorneal angle recess area (ICA).Results The mean age of the patients was 55±9.6 years (range: 40–80 years), and 12 patients were females. LPI was performed in the supero-temporal quadrant in 12 eyes and in the supero-nasal quadrant in eight eyes. On gonioscopy, none of the angle structures were seen on primary gaze in the four quadrants in two eyes, in three quadrants in eight eyes, and in two quadrants in 10 eyes. After LPI, ILCD increased significantly in 10 eyes (P<0.001), whereas AOD and ICA widened significantly in all eyes (P<0.0001). Most of the AOD widening was noted in the temporal quadrant followed by the superior quadrant. ICA increase was largest in the temporal quadrant. ILCD increased significantly with flattening of the convex iris. There was no significant change in the anterior chamber depth, lens thickness, trabecular-ciliary process distance, or iris thickness after LPI.Conclusion LPI significantly changed the morphology and parameters of anterior segment in eyes with narrow drainage angles, with obvious widening of the drainage angle. Unlike gonioscopy, these changes could be objectively highlighted and quantified accurately by UBM.