PURPOSE: To evaluate the additional intraocular pressure (IOP) lowering effect of gonioscopy-assisted transluminal trabeculotomy (GATT) to contemporary goniosynechialysis (GSL) in endeavouring to abolish subsequent occlusion after chronic iridotrabecular contact in primary angle closure (PAC) patients. METHODS: A retrospective case series of all PAC eyes underwent GATT + GSL with or without phacoemulsification and intraocular lens implantation (PEA + IOL) from December 2016 to May 2018 were recruited. IOP and the number of anti-glaucoma medications were compared pre- and post-operatively by Wilcoxon signed-rank test. Repeated measure ANOVA was used to evaluate the difference in IOP change after the operation between a subgroup of operations (GATT + GSL + PEA + IOL and GATT + GSL) and the arc of cutting of trabeculotomy. RESULTS: Thirty-nine eyes of 30 patients, 37 chronic angle closure glaucoma (CACG), 1 acute primary angle closure (APAC), and 1 plateau iris syndrome were recruited. Mean preoperative IOP was 21.8 ± 5.4 mmHg. Mean post-operative IOP was lowered to 15.1 ± 3.8 mmHg at 1 month, 14.4 ± 1.2 mmHg at 3 months, 14.8 ± 2.1 mmHg at 6 months, 14.5 ± 0.8 mmHg at 1 year, and 15 at 2 years (P < 0.001, P = 0.0012, P = 0.001, P = 0.028, and P = 0.317 (n = 1), consecutively). Mean of overall post-operative IOP at the last follow-up was 15.1 ± 4.4 mmHg (P < 0.001). Mean preoperative number of anti-glaucoma medications was 3.5 ± 1.4. Mean post-operative number of anti-glaucoma medications was reduced to 1.5 ± 1.4 at 1 month, 0.9 ± 0.9 at 3 months, 1.4 ± 1.4 at 6 months, 1.5 ± 0.5 at 1 year, and 2 at 2 years (P < 0.001, P = 0.01, P = 0.002, P = 0.028, and P = 0.317 (n = 1), respectively). Mean of overall post-operative number of anti-glaucoma medications was 1.1 ± 1.2 (P < 0.001). There was no significant difference found between the IOP lowering effect in subgroup analysis. CONCLUSION: GATT + GSL could significantly reduce IOP and number of anti-glaucoma medications from baseline compared to the last follow-up; however, there seemed not to be any superiority to the effects found in previous studies reported about GSL + PEA or PEA alone in PAC patients.