Association between Baseline Iris Thickness and Prophylactic Laser Peripheral Iridotomy Outcomes in Primary Angle-Closure Suspects

Objective To evaluate the association between baseline measurements of iris thickness at 3 positions and change in anterior segment biometric parameters after prophylactic laser peripheral iridotomy (LPI). Design Prospective clinical cohort study. Participants Fifty-two eyes of 52 nonglaucomatous subjects with anatomically narrow angles. Methods Anterior segment optical coherence tomography (ASOCT) images captured before and after LPI were analyzed using customized software, the Zhongshan Angle Assessment Program (ZAAP) (Zhongshan Ophthalmic Centre, Guangzhou, China). Differences in preoperative and postoperative measurements for anterior segment biometric parameters were compared by paired Student t tests. Multivariate linear regression models, adjusted for age, sex, ethnicity, and preoperative pupil diameter, were used to examine the association between the baseline measurements of iris thickness at 3 positions and the change in anterior segment biometric parameters after LPI. Main Outcome Measures Baseline iris thickness measured at 750 μm from the scleral spur (IT750), iris thickness measured at 2000 μm from the scleral spur (IT2000), and maximal iris thickness (ITM). Changes in iris curvature (ICURV) and trabecular–iris space area at 500 μm from the scleral spur (TISA500) and 750 μm from the scleral spur (TISA750) after LPI. Results The ICURV significantly decreased, whereas TISA500 and TISA750 significantly increased after LPI (all P