Background <p>Phacoemulsification combined with intraocular lens implantation and goniosynechialysis (PEI + GSL) represents a mainstream ​surgical technique​for the treatment of primary angle-closure glaucoma (PACG). As the disease progresses, when the extent of peripheral anterior synechiae (PAS) gradually expands to 360°, whether PEI + GSL remains effective remains uncertain. This study aimed to investigate the long-term clinical efficacy​of PEI + GSL in treating PACG patients with 360° PAS.</p> Methods <p>A case‒control study was conducted on PACG patients with 360° PAS (360° PAS group) and those with PASs ranging from 90° to 180° (90°≤ PAS ≤ 180° group). Patients underwent PEI + GSL and were followed up for 1–3 years. The data collected included intraocular pressure (IOP), glaucoma medications, visual acuity, PAS extent, complications, and other relevant parameters. Kaplan‒Meier curves were used to analyse the cumulative surgical success rates in both groups.</p> Results <p>The 360° PAS group included 31 eyes (31 patients), and the 90°≤ PAS ≤ 180° group included 32 eyes (32 patients). At the final follow-up (36 months), the IOP was 14.8 ± 3.9 mmHg in the 360°PAS group and 15.5 ± 2.9 mmHg in the 90°≤ PAS ≤ 180° group (<i>P</i> = 0.507). The degree of IOP reduction was 47.9% in the 360°PAS group and 33.0% in the 90°≤ PAS ≤ 180° group (<i>P</i> = 0.272). The mean number of glaucoma medications decreased by 2.5 in the 360°PAS group and 1.1 in the 90°≤ PAS ≤ 180° group (<i>P</i> &lt; 0.001). The complete plus qualified success rates at 3 years were 90.3% and 93.8%, respectively, with no significant difference (<i>P</i> = 0.970).</p> Conclusions <p>PEI + GSL in PACG patients with 360° PAS resulted in a 47.9% reduction in IOP, a mean reduction of 2.5 glaucoma medications, and a high overall surgical success rate (90.3%), comparable to the 90°≤ PAS ≤ 180° group (93.8%).</p> Trial registration <p>ChiCTR2400086966 The study protocol was approved in the Chinese Clinical Trial Registry at 2024-07-16.</p>