AIM: To investigate the safety and efficacy of the Zeiss Visulas II diode laser system in the reduction of intraocular pressure (IOP) in patients with complex glaucoma. METHODS: The authors analysed the medical records of patients who underwent trans-scleral diode laser cycloablation (TDC) at the Manchester Royal Eye Hospital during a 34 month period. 55 eyes of 53 patients with complex glaucoma were followed up for a period of 12-52 months (mean 23.1 months) after initial treatment with the Zeiss Visulas II diode laser system. RESULTS: Mean pretreatment IOP was 35.8 mm Hg (range 22-64 mm Hg). At the last examination, mean IOP was 17.3 mm Hg (range 0-40 mm Hg). After treatment, 45 eyes (82%) had an IOP between 5 and 22 mm Hg; in 46 eyes (84%) the preoperative IOP had been reduced by 30% or more. The mean number of treatment sessions was 1.7 (range 1-6). At the last follow up appointment, the mean number of glaucoma medications was reduced from 2.1 to 1.6 (p<0.05). In 10 eyes (18%), post-treatment visual acuity (VA) was worse than pretreatment VA by 2 or more lines. CONCLUSIONS: Treatment with the Zeiss Visulas II diode laser system can be safely repeated in order to achieve the target IOP. Treatment outcomes in this study were similar to those from previously published work using the Iris Medical Oculight SLx laser.