Progressive Changes in the Anterior Segment and Their Impact on the Anterior Chamber Angle in Primary Angle Closure Disease

Abstract

To investigate longitudinal changes in the anterior segment (AS) using serial optical coherence tomography (OCT) images and determine impact of these changes on the anterior chamber angle (ACA) in eyes with primary angle closure disease (PACD) treated with laser peripheral iridotomy (LPI). Retrospective clinical cohort study. This study included 103 patients with PACD who underwent LPI and were followed-up by a mean 6.7 ± 1.7 AS-OCT examinations for a mean 6.5 ± 2.9 years. Temporal changes in AS-OCT parameters, including anterior chamber depth (ACD), angle opening distance (AOD750), angle recess area (ARA750), iris thickness (IT750), lens vault (LV), and pupil diameter (PD), were analyzed by multivariate linear mixed effects models (LMEMs). Multivariate LMEMs showed that decrease in AOD750 was not significant (-1.59 μm/yr, p = 0.222), however, ARA750 decreased over time (-2.3 × 103 μm2/yr, p = 0.033) and SSA showed marginal significance (-0.20°/yr, p = 0.098), and LV increased significantly (11.6 μm/year, p < 0.001) after LPI. Mean LV change was negatively associated with AOD750, ARA750 and SSA, while PD was negatively associated with ARA750 (p < 0.001 each). PD decreased with aging (-13.7 μm/year, p = 0.036) accompanied by thinning of IT750 (-1.7 μm/year, p = 0.063). LV tends to increase with aging which contributes to the shallowing of the anterior chamber and narrowing of ACA in PACD eyes treated with LPI. In the meantime, pupillary constriction and subsequent peripheral iris thinning associated with aging could possibly offset the effect of ACA narrowing.