Nonpenetrating glaucoma surgery: Meta-analysis of recent results

Purpose: To evaluate the efficacy of nonpenetrating glaucoma surgery for open angle glaucoma with respect to target intraocular pressure (IOP) and severity of glaucoma. Materials and Methods: A literature search with the terms "nonpenetrating glaucoma surgery, deep sclerectomy (DS), viscocanalostomy (VC), and open angle glaucoma" was carried out for the reports in the last 5 years. Studies encompassing only combined glaucoma and cataract surgery were excluded. Measurement of effectiveness was determined on the basis of achievement of target IOP. Data related to postoperative goniopuncture and needling with antimetabolite application were noted. Results: The percentage of cases achieving <= 21 mm Hg was 48.6% after primary DS, 68.7% after DS with implant, 67.1 % after DS with antimetabolite, 51.1% after primary VC, and 36.8% after VC with antimetabolite or implant. Visual field parameters were almost exclusively not available; whereas cup/ disk ratio and target IOP lower than 21 mm Hg were available in very few reports. With lower set IOP targets, the rates of success varied between 35% and 86% for DS, and between 10% and 67% for VC. The mean follow-up of the studies were mostly in the range of 3 years. Conclusions: Nonpenetrating glaucoma surgery seems to provide IOP reduction into the high teens. Its potential to achieve lower target IOPs seems to be low. Longer-term studies, with data related to glaucoma severity and proper target IOPs are required.