Low Iris and Anterior Chamber Volume is Associated with Deepening after Laser Peripheral Iridotomy in Primary Angle Closure Suspects

Purpose: To evaluate the association between baseline ocular variables and the widening of the anterior chamber angle by laser peripheral iridotomy (LPI) in primary angle closure suspects (PACS) using a new Fourierdomain swept-source anterior segment optical coherence tomography (FD-ASOCT). Methods: Sixty-six PACS eyes of 41 individuals were enrolled in this prospective interventional case series. An FD-ASOCT (Casia SS-1000 OCT; Tomey, Nagoya, Japan) was used to measure biometric baseline variables andat one month after the LPI. Paired t-test was used to compare the difference between pre-and post-LPI measurements. Multivariate regression analysis was used to test for an association between baseline iris thickness and volume, anterior chamber depth and volume, and lens vault with a widening of the angle after an LPI. Changes in trabecular iris space area and angle opening distance after the LPI were main outcome measures. Results: The mean age of participants was 58.6±8.7 years, 68.2% of whom were female. The angle opening distance, recess area and trabecular iris surface area at 500 microns increased by 48% to 73% (all p<0.001). Lens vault and iris volume did not change. A low anterior chamber volume and low iris volume were associated with angle greater deepening by LPI. Conclusion: Eyes with a shallow anterior chamber and thinner irises are more likely to experience angle opening from an LPI.