Changes in Anterior Segment Parameters After Laser Peripheral Iridotomy in Caucasian Eyes With Different Primary Angle Closure Mechanisms

Abstract

Précis: Subgrouping of angle closure mechanisms based on the swept-source optical coherence tomography images may help to identify the predominant underlying anatomic mechanism, evaluate personal treatment, and improve the better outcomes. Purpose: The purpose of this study was to evaluate changes in anterior segment parameters in Caucasian eyes with different angle closure mechanisms before and after laser peripheral iridotomy (LPI). Methods: Sixty-six subjects underwent swept-source optical coherence tomography (CASIA, Tomey Corporation) angle imaging in the dark before and 7 days after LPI. On the basis of the baseline swept-source optical coherence tomography images, the eyes were categorized into 4 angle closure mechanisms, namely pupillary block (PB), plateau iris configuration (PIC), thick peripheral iris (TPI), and large lens vault (LLV). Sixteen out of 128 cross-sectional images (11.25 degrees apart) per volume scan were selected for analysis. We used a generalized estimating equation to compare quantitative parameters among angle closure mechanisms and between before and after LPI after adjusting the intereye correlation. Results: The mean age of subjects was 67.7±9.2 years, with the majority being female (82.2%). One hundred twenty-nine eyes (67 primary angle closure suspects, 34 primary angle closure, and 28 primary angle closure glaucoma) were categorized into PB (n=71, 55%), PIC (n=40, 31%), TPI (n=14, 10.9%), and LLV (n=4, 3.1%). Anterior chamber depth was the shallowest in the LLV, followed by TPI, PB, and PIC group at baseline. Widening of the angle and reduction of the iris curvature (IC) due to LPI were observed in all groups (all P<0.01). When compared to the PB group, the LPI-induced angle widening in the TPI group was significantly less even though the iris curvature reduction in the TPI group was greater (all P<0.05). Conclusions: In patients with angle closure, anterior segment morphology and LPI-induced angle widening were different among the various angle closure mechanisms.