Smaller Anterior Chamber Volume Is Associated With Higher Risk of Intraocular Pressure Elevation After Laser Peripheral Iridotomy: A 1-Year Follow-Up Study

Purpose: The aim of this study was to analyze the predictive value of swept-source optical coherence tomography (SS-OCT) derived anterior-segment volumetric parameters such as anterior chamber volume (ACV) in the long-term follow-up of primary angle closure disease (PACD). Design: Longitudinal observational study. Methods: In this single-center longitudinal observational study, PACD patients undergoing laser peripheral iridotomy (LPI) were recruited. Anterior segment images of the patients were captured using SS-OCT before LPI, and at 1 week, 1 month, 3 months, 6 months, and 1 year after LPI. Ninety eyes of 81 subjects were enrolled, and 72 eyes of 72 subjects finished the 1 year follow-up. Data of all the 81 subjects were included for analysis. Intraocular pressure (IOP) elevation was defined as IOP >21 mm Hg at any time point after LPI. The association between baseline trabecular-iris space area 750 mu m from scleral spur (TISA750), ACV and iris volume (IV), and IOP elevation were analyzed using logistic regression. Results: Eighty-one subjects were included, 59 were female, and 22 were male, with a mean age of 60.98 +/- 9.44 years. IOP elevation appeared in 14 eyes. Mean TISA750 was negatively associated with IOP elevation (OR = 0.94, P = 0.02). The correlation of TISA750 with IOP elevation varies across quadrants and there was only significant association in temporal TISA750 (OR - 0.98, P - 0.046), whereas in the other 3 quadrants, there was no significant association. Greater ACV was associated with lower risk of IOP elevation (OR = 0.80, P= 0.031), whereas IV was not associated with IOP elevation. Conclusions: ACV is a reliable and accurate predictor for the outcome of PACD. Due to its 3-dimensional nature, the robustness of ACV is greater than traditional angle width parameters such as TISA750.