Abstract:  Objective To observe the impact of early intervention with YAG laser peripheral iridotomy (LPI) on high-risk patients of primary angle clouse glaucoma (PACG). Design Cohort study． Participants 52 patients (104 eyes) with high-risk PACG. Method The patients with high-risk PACG were randomly divided into two groups. One group [26 patients (52 eyes)] was treated with LPI, and another group ［26 patients (52 eyes)］ was control group in which, the patients wasn't given any intervention. Following up for 2 years, routine ophthalmic examination and UBM were performed at the first visit (before LPI), 2 weeks, 6, 12 months and 2 years after LPI, respectively. The parameters of anterior chamber were measured and calculated by UBM. Main Outcome Measures Intraocular pressure(IOP), the parameters of anterior chamber measured by UBM. Results The average postoperative IOP in the intervention group was (15.20±2.39) mm Hg in the final follow-up, which was lower than pre-operation (16.89±3.01 mm Hg); The central anterior chamber depth, the mean angle-opening distance, the trabecular iris angle and the mean chamber angle width was increased after LPI (all P＜0.01). There was no significant change in IOP in the control group  at 12 months visit (P＞0.05), but  the angle-opening distance, the trabecular iris angle and the mean chamber angle width was decreased (all P＜0.05)； The average intraocular pressure in the control group was (17.31±2.27) mm Hg in the final follow-up, which was higher than pre-operation (P＜0.05); there were two cases (2 eyes) suffered PACG acute attacks in control group, while there was no PACG in the intervention group after two year's follwing up. Conclusion LPI can effectively prevent the development of high-risk PACG to PACG and improve the anterior chamber and anterior chamber angle structures.

Key words: primary angle clouse glaucoma/laser therapy; , ultrasound biomicroscopy