RATIONALE: Glaucoma is the leading cause of irreversible blindness. Minimally invasive glaucoma surgery (MIGS) techniques, including those that open or enlarge Schlemm's canal (SC) behind the trabecular meshwork (SC-MIGS), have been introduced to help optimise control of intraocular pressure (IOP), which may slow the progression of glaucoma. This review supersedes and expands on the scope of a previous Cochrane review on ab interno trabecular bypass surgery with Trabectome for open-angle glaucoma. OBJECTIVES: To assess the effects of minimally invasive Schlemm's canal surgery in comparison to medical, laser, or surgical treatment (including other MIGS techniques) in people with open-angle glaucoma. SEARCH METHODS: We used CENTRAL, MEDLINE, Embase, two other databases, and trial registries, together with reference checking, citation searching, and contact with study authors, to identify studies that are included in the review. The latest search date was 12 October 2025. ELIGIBILITY CRITERIA: We searched for randomised controlled trials (RCTs) comparing SC-MIGS with other treatments (other MIGS, laser, phacoemulsification, or medical therapy). Reported SC-MIGS procedures included gonioscopy-assisted transluminal trabeculotomy, ab interno canaloplasty, Kahook Dual Blade goniotomy, excimer laser trabeculotomy, and ab interno trabeculectomy. We excluded studies of non-SC-MIGS (e.g. iStent inject, Hydrus, or other microstents), conventional non-MIGS glaucoma surgery (e.g. trabeculectomy), and non-MIGS laser procedures (e.g. selective laser trabeculoplasty (SLT)). We included studies where procedures were combined with phacoemulsification and compared to phacoemulsification in combination with other glaucoma surgery or phacoemulsification alone. OUTCOMES: Critical outcomes were the proportion of participants medication-free at each time point and the rate of visual field progression (decibels/time) or proportion of participants whose visual field loss progressed during follow-up. Important outcomes included mean change in IOP; mean change in IOP-lowering drops taken per day; proportion of participants requiring further glaucoma surgery or laser; and mean change in health-related quality of life. Adverse event outcomes included loss of visual acuity, bleeding, endophthalmitis, and IOP spikes. All outcomes were measured in the short term (6 to 18 months), medium term (> 18 to 36 months), and long term (> 36 months or longer). RISK OF BIAS: We assessed risk of bias using the Cochrane RoB 2 tool. SYNTHESIS METHODS: We used standard Cochrane methodology. We undertook meta-analysis where the data appeared to be clinically, methodologically, and statistically homogeneous. We used a random-effects model when there were three or more studies, otherwise we used a fixed-effect model. Where we could not perform a meta-analysis due to high heterogeneity, we provided a narrative summary of the data following guidance in the Cochrane Handbook. INCLUDED STUDIES: We included 10 parallel-group RCTs (639 participants). The mean age ranged from 41 to 74 years, and the proportion of male participants from 25% to 74%. Ethnicity was reported in five studies (Japanese (two), Caucasian/white (one), various ethnicities (two)). One study was multicentre and one multinational; the remainder were single-centre studies. Studies were conducted in Italy (two), Japan (two), and India, the United States and Latin America, Poland, Canada, and China (one each). SYNTHESIS OF RESULTS: = 39%; 2 studies; very low-certainty evidence), IOP change (without phacoemulsification: mean difference (MD) -0.75 mmHg, 95% CI -2.85 to 1.35; 1 study; low-certainty evidence; with phacoemulsification: MD 3.70 mmHg, 95% CI -3.25 to 10.65; 1 study; very low-certainty evidence), change in IOP-lowering drops per day (with phacoemulsification: MD -0.71, 95% CI -1.79 to 0.37; 1 study; very low-certainty evidence), further surgery (with phacoemulsification: RR 2.70, 95% CI 0.13 to 58.24; 2 studies; very low-certainty evidence), or adverse events. One study narratively reported that there were no changes in the rate of visual field progression. For comparison 2 (SC-MIGS with phacoemulsification versus phacoemulsification only), in the short term, SC-MIGS may increase medication-free participants (RR 105.00, 95% CI 6.64 to 1660.79; 1 study; low-certainty evidence) and result in a greater mean IOP change (MD -8.70 mmHg, 95% CI -10.12 to -7.28; 1 study; low-certainty evidence). There was no evidence of a difference in further surgery (RR 0.33, 95% CI 0.02 to 7.24; 1 study; very low-certainty evidence). SC-MIGS may increase bleeding risk (RR 13.42, 95% CI 1.86 to 96.98; 2 studies; low-certainty evidence), with no evidence of a difference in other adverse events. For comparison 3 (SC-MIGS versus non-SC-MIGS), there was no evidence of a difference in medication-free participants (RR 1.07, 95% CI 0.92 to 1.24; 2 studies; very low-certainty evidence), IOP change (MD -0.25, 95% CI -1.13 to 0.63; 2 studies; very low-certainty evidence), change in IOP-lowering drops per day (MD -0.15, 95% CI -0.34 to 0.03; 2 studies; very low-certainty evidence), further surgery (no participants in either group), or adverse events. Comparison 4 (SC-MIGS versus other SC-MIGS) showed there were likely no differences between the groups in nearly all outcomes. Comparison 5 (SC-MIGS versus laser) showed there may be a greater reduction in mean IOP, but there may be a greater risk of bleeding in the SC-MIGS group. AUTHORS' CONCLUSIONS: The available evidence is of low or very low certainty, and we are therefore able to draw only weak, uncertain conclusions about the effects of SC-MIGS. There may be little to no difference in the proportion of participants who are medication-free in the short, medium, or long term between SC-MIGS and non-MIGS surgical treatment. SC-MIGS may demonstrate a higher proportion of participants to be medication-free in the short term compared to phacoemulsification surgery alone; however, there may be a higher risk of bleeding. SC-MIGS may also be associated with a greater reduction in mean IOP compared to laser treatment. FUNDING: This Cochrane review was supported by the National Eye Institute, National Institutes of Health, USA; Public Health Agency, UK; Queen's University Belfast, UK; National Institute for Health Research, UK until March 2023. REGISTRATION: Protocol (2022): doi.org/10.1002/14651858.CD015186.
Vemulapalli et al. (2026) studied this question.