Vol 33 No. 2 Original Article PDF

Ultrasound biomicroscopy outcomes after laser peripheral iridotomy in narrow occludable angles

Mary Ruth M. Quilendrino, MD, Patricia M. Khu, MD, Margarita Lat-Luna, MD

This study characterized the features of narrow occludable angles (NOA) using ultrasound biomicroscopy (UBM) before and after laser peripheral iridotomy (LPI).

A prospective interventional study was conducted involving patients diagnosed with NOA or who were primary angle-closure suspects (PACS). UBM was performed before and 2 weeks after LPI. Van-Herick and Schaffer gradings were used to assess the limbal-chamber depth (LCD) and angles respectively. Quantitative and qualitative changes in UBM parameters before and after LPI were measured. Data comparing pre- and post-LPI parameters were analyzed.

Included were 34 eyes of 22 patients with a mean age of 62 ± 8 years. Nine out of 10 patients were females. LCD increased significantly after LPI (p < 0.0001). The Shaffer angle grading on static gonioscopy widened significantly in all quadrants after LPI (p < 0.05). The largest change in angle width was noted in the inferior quadrant (30%). Angle-opening distance (AOD) 250, AOD 500, and iridocorneal angle (ICA) widened significantly (p < 0.0001) after LPI. The greatest amount of AOD widening was in the nasal quadrant. Iridocorneal angle increase was largest in the superior quadrant. There was no statistically significant change in anterior-chamber depth (ACD), lens thickness, ciliary-body thickness, and iris thickness before and after LPI. There was also no statistically significant difference in any of the quantitative UBM parameters between eyes with clinically open or closed angles 2 weeks after LPI.

Although LPI did not always result in clinically open angles, UBM demonstrated a significant increase in angle width in patients with NOA or PACS. Keywords: Ultrasound biomicroscopy, Laser peripheral iridotomy, Narrow occludable angles, Primary angle-closure suspect, Angle opening distance, Gonioscopy