Background: To evaluate the intraocular pressure (IOP)-lowering effects achieved by nonpenetrating glaucoma surgery (NPGS) and its modifications in patients with open angle glaucoma.
Material/Methods: Randomized controlled trials evaluating patients with primary and secondary open angle glaucoma treated with NPGS were identified through systematic searches. The main outcome measures were the percentage IOP reduction and the complete success rate. Complete success was defined as target endpoint IOP (usually less than 21 mm Hg) without medications. The pooled estimates were calculated using the random effects model.
Results: Both deep sclerectomy (DS) and viscocanalostomy (VCO) were less effective than trabeculectomy (TE) in lowering IOP, with the percentage IOP reductions at 2 years being 35.2% for DS, 30.2% for VCO, and 45.6% for TE. Intraoperative use of implants and mitomycin C (MMC) increased IOP-lowering effects of DS, with IOP reductions at 2 years of 41.1% and 41.7%, respectively. The complete success rates at 4 years were 35.4% for DS, and 22.7% for VCO, lower than that of TE (47.6%). The complete success rates of DS with implants and MMC of 64.6% and 52.1%, respectively, at 4 years, were greater than that of primary DS. NPGS caused major complications in fewer patients than did TE.
Conclusions: Primary deep sclerectomy and primary viscocanalostomy, which can significantly lower IOP, were associated with fewer complications than was TE. However, the IOP-lowering effects of both NPGS seem to be lower than that of primary TE. The efficacy of DS can be improved with the intraoperative use of implants and MMC.

Keywords: Intraocular Pressure - physiology, Mitomycin - therapeutic use, Glaucoma, Open-Angle - surgery, Filtering Surgery - methods