Longitudinal Changes in Anterior Segment Parameters After Laser Peripheral Iridotomy Assessed by Anterior Segment Optical Coherence Tomography

Abstract

To quantify long-term changes in anterior segment (AS) parameters after laser peripheral iridotomy (LPI) using AS optical coherence tomography (OCT) in primary angle-closure suspect (PACS). Thirty-two PACS subjects were imaged at pre-LPI and 2 weeks and 18 months post-LPI using AS OCT. Anterior chamber depth (ACD), iris curvature (IC), iris thickness at 750 and 1500 μm from the scleral spur (IT750, 1500), lens vault (LV), anterior chamber area (AA), and iris area (IA) were estimated by ImageJ software (version 1.46). Anterior chamber angle (ACA) parameters (angle opening distance [AOD750], angle recess area [ARA750], and trabecular iris space area [TISA750]) were provided by the manufacturer. Parameters were compared before and after LPI. Uni- and multivariate regression analysis was performed to evaluate factors associated with ACA narrowing. Mean AA (14.63 vs. 15.87 mm(2)) and three ACA parameters (AOD750 [0.17 vs. 0.28 mm], TISA750 [0.07 vs. 0.11 mm(2)], and ARA750 [0.08 vs. 0.13 mm(2)]) increased at 2 weeks post-LPI (all P < 0.001). The IT750, 1500 and IC also showed change at 2 weeks post-LPI. Eighteen months post-LPI, IC (0.34 vs. 0.16 mm, P < 0.001) and LV (0.88 vs. 1.01 mm, P = 0.001) were significantly different, while three ACA parameters were not different from their pre-LPI status. At post-LPI 18 months, LV was significantly associated with ACA narrowing (P = 0.026). The ACA tended to be narrowed at 18 months post-LPI despite resolution of pupillary block, which may be due to LV increment. Our results warrant continuous follow-up of narrow-angle patients after LPI.