PURPOSE: To study prospectively the success rate and complications of deep sclerectomy with collagen implant (DSCI), a nonpenetrating filtration procedure, in patients with glaucoma and high myopia. SETTING: Glaucoma Unit, Hôpital Ophtalmique Jules Gonin, Lausanne, Switzerland. METHODS: This nonrandomized prospective trial comprised 21 eyes of 21 highly myopic patients with medically uncontrolled primary or secondary open-angle glaucoma. Visual acuity, intraocular pressure (IOP), and slitlamp examinations were performed before as well as 1 and 7 days and 1, 3, 6, 9, 12, 18, 24, 30, 36, 42, 48, 54, 60, and 66 months postoperatively. Visual field examinations were repeated every 6 months. Exclusion criteria were known allergy to collagen, advanced lens opacity, and eye surgery or laser trabeculoplasty fewer than 6 months before enrollment. RESULTS: The mean follow-up was 44.0 months +/- 17.1 (SD). The mean preoperative IOP of 26.4 +/- 5.9 mm Hg dropped to 10.4 +/- 6.1 mm Hg at 48 months. Eighty-one percent of patients achieved an IOP below 21 mm Hg with or without medication at 48 months. Thirty-eight percent had an IOP below 21 mm Hg without medication. The mean number of medications per patient was reduced from 2.30 +/- 0.85 to 0.86 +/- 0.91. CONCLUSIONS: Deep sclerectomy with collagen implant provided reasonable control of IOP in patients with glaucoma and high myopia over a long-term follow-up. There were relatively few postoperative complications.