Novel Discoveries of Anterior Segment Parameters in Fellow Eyes of Acute Primary Angle Closure and Chronic Primary Angle Closure Glaucoma

PURPOSE: To investigate the biometric differences of anterior segment parameters between fellow eyes of acute primary angle closure (F-APAC) and chronic primary angle closure glaucoma (F-CPACG) to get information about differences between APAC and CPAC. METHODS: Patients with F-APAC and F-CPACG without prior treatment were enrolled from glaucoma clinics. Parameters were measured on ultrasound biomicroscopy images, including pupil diameter, lens vault (LV), anterior chamber depth, anterior chamber width, iris area, iris thickness (IT 750 and 2000), angle-opening distance (AOD 500 and 750), trabecular-iris space area (TISA 500 and 750), trabecular iris angle (TIA 500 and 750), trabecular–ciliary angle, and ciliary process area. Multivariate logistic regression analysis was performed to determine the most important parameters associated with F-APAC compared with F-CPACG. RESULTS: Fifty-five patients with APAC and 55 patients with CPACG were examined. The anterior chamber depth, IT 750, AOD 750, trabecular iris angle 750, and trabecular–ciliary angle were smaller, and LV and ciliary process area were greater in F-APAC as compared with F-CPACG (P ≤ 0.01). Multivariate logistic regression showed that thinner IT 750, smaller AOD 750, and larger LV were significantly associated with F-APAC (P < 0.01). IT 750 (area under the curve, 0.703) performed relatively better than AOD 750 (area under the curve, 0.696) in distinguishing F-APAC from F-CPACG, with the best cutoff of 0.404 mm and 0.126 mm, respectively. CONCLUSIONS: Compared with F-CPACG, F-APAC had thinner peripheral iris, narrower anterior chamber angle, shallower anterior chamber depth, greater LV, larger and anteriorly positioned ciliary body. IT 750, AOD 750, and LV played important roles in distinguishing eyes predisposed to APAC or CPAC.