AIM: To identify the value of using collagen implant in deep sclerectomy. METHODS: A prospective randomised trial of 104 eyes (104 patients) with medically uncontrolled primary and secondary open angle glaucoma. All patients had deep sclerectomy (DS), half of them with and the other half without a collagen implant (CI) sutured in the scleral bed. The main outcome measures were intraocular pressure (IOP), visual acuity, number of treatments preoperative and postoperative, and Nd:YAG goniopunctures. RESULTS: Mean follow up period was 44.5 (SD 21) months for the DS group and 43.9 (SD 14) months for the deep sclerectomy with a collagen implant (DSCI) group. The mean preoperative IOP was 23.3 (SD 7.2) mm Hg for the DS group and 25.6 (SD 4.9) mm Hg for the DSCI group. The mean IOP at the first postoperative day was 6.1 (SD 4.21) mm Hg for the DS group and 5.1 (SD 3.3) mm Hg for the DSCI group. At 48 months IOP was reduced by 40% (14 versus 23.3 mm Hg) for the DS group and by 50% (12.7 versus 25.6 mm Hg) for the DSCI group. Complete success rate, defined as IOP lower than 21 mm Hg without medication, was 34.6% (18/52 patients) at 48 months for the DS group, and 63.4% (33/52 patients) for the DSCI group. Qualified success rate; patients who achieved IOP below 21 mm Hg with or without medication, was 78.8% (41/52 patients) at 48 months and 94% (49/52 patients) for the DSCI group. The mean number of medications was reduced from 2.1 (SD 0.8) to 1.0 (SD 1) after DS, and was reduced from 2.2 (SD 0.7) to 0.4 (SD 0.6) in the DSCI group (p = 0.001) CONCLUSION: The use of a collagen implant in DS enhances the success rates and lowers the need for postoperative medication.