[Differences in anterior segment structure and pupillary diastolic characteristics of eyes with primary angle closure...

Objective: To investigate the anatomical structure changes of the anterior segment and dynamic pupil changes in eyes with suspected primary angle-closure (PACS) under light and dark conditions, and their correlation with the occurrence of acute primary angle-closure (APAC). Methods: This cross-sectional study collected data from 37 PACS patients (66 eyes) who visited the ophthalmology clinic of the Second Affiliated Hospital of Harbin Medical University between September 2019 and March 2021. The patients included 12 males and 25 females, with an average age of (61.27±7.35) years. Of the 66 eyes, 58 had no history of APAC in the contralateral eye, while 8 had a history of APAC in the contralateral eye. Patients without a history of APAC in both eyes underwent the dark room prone provocative test (DRPPT), and the eyes were divided into three groups: DRPPT- (44 eyes), DRPPT+ (14 eyes), and APAC (8 eyes). The DRPPT+ and APAC groups were combined into the APAC+ group. All patients underwent ultrasound biomicroscopy (UBM) to measure the changes in various parameters under light and dark conditions, including anterior chamber angle 500 (ACA_500Δ) and 1000 (ACA_1000Δ), angle opening distance 500 (AOD_500Δ) and 1000 (AOD_1000Δ), and iris thickness 500 (IT_500Δ) and 1000 (IT_1000Δ). Anterior segment analysis was performed to capture the pupil changes under light and dark conditions, recording pupil diameter, maximum dilation speed (V_max), maximum constriction speed (V_min), and average speed (V_m). Results: There was no significant difference in the parameters between DRPPT+ group and APAC group (P>0.05). In the difference analysis, it was found that the V_m value of DRPPT- group [(0.17±0.07) mm/s] was higher than that of APAC+ group [(0.13±0.06)mm/s], and the difference was statistically significant (P<0.05). There was no significant difference in other parameters (P>0.05). V_max was positively correlated with temporal ACA_1000Δ and temporal AOD_1000Δ in all patients with PACS (r=0.302, 0.260; P<0.05), V_min was negatively correlated with temporal ACA_1000Δ and temporal AOD_1000Δ (r=-0.338, -0.330; P<0.05). Conclusions: The dynamic changes in the anterior segment and pupil under different lighting conditions provide insights into the risk factors and potential predictive indicators for the occurrence of APAC in PACS patients.