Aims: To prospectively evaluate by ultrasound biomicroscopy (UBM) and gonioscopy the anterior chamber angle widening following laser peripheral iridotomy (LPI) in eyes with early chronic primary angle closure glaucoma (CACG).
Methods: A total of 55 eyes of 55 patients with CACG presenting with less than 180 degrees peripheral anterior synechiae (PAS) were enrolled in the study. Angles were assessed by gonioscopy (Shaffer's grading) and UBM, before and 4 weeks after LPI. The angle opening distance at 250 and 500 microm from the scleral spur (AOD 250 and AOD 500) was computed. Results were analysed using the Wilcoxon signed-rank test.
Results: In the quadrant with LPI, the mean gonioscopy grade increased significantly from 0.45 to 1.45 (P<0.001) and the mean AOD 250 and AOD 500 increased from 38.5+/-25.9 to 83.5+/-48.4 microm (P<0.001) and 110.2+/-80.9 to 170.6+/-83.4 microm (P<0.001), respectively. The angles widened significantly in the opposite quadrant on UBM (AOD 250: 48.8+/-31.5-82.7+/-43.9 microm, P<0.001; AOD 500:117.2+/-65.5-172.2+/-81.7 microm; P<0.001), but the median gonioscopy grade remained unchanged.
Conclusions: LPI significantly widened the anterior chamber angle in the quadrant with LPI and the quadrant furthest away in patients of CACG with established glaucomatous damage. This change was much better appreciated by the UBM than gonioscopy.