To evaluate the intraocular pressure (IOP)-lowering efficacy of goniosynechialysis (GSL) for advanced chronic angle-closure glaucoma (CACG) using a simplified slit-lamp technique.Patients with CACG with one severely affected eye with best-corrected visual acuity below 20/200 and a mildly or functionally unaffected fellow eye were enrolled in this study. All patients underwent ophthalmologic examinations including measurement of visual acuity, best-corrected visual acuity, and IOP; biomicroscopy; specular microscopy; fundus examination; and gonioscopy followed by anterior chamber paracentesis and GSL for nasal peripheral anterior synechiae in the eye with severe CACG.Thirty patients (18 men, 12 women) were identified as having CACG with an initial mean IOP of 47.1 ± 6.7 mmHg (range 39-61 mmHg) in the severely affected eye. One week after GSL, the mean IOP of the treated eyes decreased to 19.3 ± 2.8 mmHg (range 14-26 mmHg) without antiglaucoma medication (average decrease 27.7 ± 6.5 mmHg; range 16-41 mmHg), which was significant (P < 0.00001) compared with baseline. After an average follow-up period of 36.6 ± 1.0 months (range 35-38 months), the mean IOP stabilized at 17.4 ± 2.2 mmHg (range 12-21 mmHg). The nasal angle recess did not close again in any one of the patients during the follow-up period. The average significant (P < 0.00001) decrease in corneal endothelial cell density in the treated eyes was 260 ± 183 cells/mm(2) (range 191-328 cells/mm(2)).Anterior chamber paracentesis and GSL lowers IOP in advanced CACG, though it may lead to mild corneal endothelial cell loss.