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 Fourier-domain swept-source anterior segment optical coherence tomography (FD-ASOCT). Method 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 and at 1 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 μm 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.