LAUSR

The mechanism of primary angle closure disease (PACD) has been extensively investigated, while some cases remain unexplained. Hypothesizing that chronic primary ciliary block (CB) may play a role in PACD pathogenesis and the contribution could be revealed by pharmacologic cycloplegia and mydriasis, this study analyzed changes in anterior segment biometric parameters following cycloplegic intervention. A total of 170 eyes of 170 Chinese subjects aged between 50 and 80 years were included: 90 in the primary angle closure suspect (PACS) group, 33 in the primary angle closure (PAC)/PAC glaucoma (PACG) group, and 47 in the normal control group. All participants underwent a comprehensive ophthalmic examination, and ultrasound biomicroscopy (UBM) was conducted in patients with PACD at the baseline. Compound tropicamide (Mydrin P, Santen, Osaka, Japan) was administered to patients for pupillary dilation. Intraocular pressure (IOP) measurement and IOLMaster were performed before and 45 min after mydriasis. Following dilation, PACS and PAC/PACG eyes demonstrated less significant changes in the anterior section compared to normal eyes based on △ACD-△LT (the difference in the changes of anterior chamber depth and lens thickness) (P < 0.01). Nine PACD eyes had a △ACD-△LT greater than 0.10 mm (1 PAC/PACG and 8 PACS eyes). About 8.94% of PACD eyes exhibited an elevated post-IOP. In PACS eyes, significantly higher pre-IOP (P < 0.05), shallower anterior chamber (AC, P < 0.01), more anterior lens position (P < 0.01), and narrower anterior chamber width (ACW, P < 0.05) were observed. A minority of PACD eyes displayed obvious movement of the ciliary-lens diaphragm, suggesting that primary CB may be an infrequent occurrence in PACD eyes. Additionally, higher IOP, shallower AC, more anteriorly placed lens, and smaller ACW may facilitate the identification of IOP spikes following dilation in clinical practice.