What minimally invasive glaucoma surgeries (MIGS) are available for glaucoma?

Available MIGS for Glaucoma

Multiple MIGS devices are currently available for glaucoma treatment, categorized by their mechanism of action: trabecular meshwork/Schlemm's canal procedures (iStent, Hydrus, Trabectome, ab interno trabeculotomy), subconjunctival drainage (Xen gel stent), and suprachoroidal shunts (CyPass—now recalled). 1, 2

Trabecular Meshwork/Schlemm's Canal-Based MIGS

iStent (Trabecular Microbypass Stent)

• FDA-approved specifically for implantation in combination with cataract extraction in patients with mild to moderate open-angle glaucoma 1, 3
• Heparin-coated titanium snorkel-shaped device implanted into Schlemm's canal under gonioscopic guidance 1
• Provides modest IOP reduction with postoperative pressures typically in the mid to upper teens 1
• Evidence shows small reduction in IOP and medication burden when combined with phacoemulsification compared to phacoemulsification alone 1
• Recent studies suggest multiple stents may provide better IOP lowering than a single stent, though guidelines typically limit coverage to maximum of two stents 1, 3
• Very low-quality evidence overall for effectiveness 1, 4

Hydrus Microstent

• Moderate certainty evidence indicates adding Hydrus to cataract surgery safely improves likelihood of drop-free glaucoma control at medium-term (RR 1.6) and long-term (RR 1.6) follow-up 5
• Confers 2.0 mm Hg greater IOP reduction at long-term follow-up compared to cataract surgery alone 5
• Randomized trial data associate Hydrus with greater drop-free glaucoma control and IOP lowering than iStent, though effect sizes were small 5

Trabectome (Ab Interno Trabeculectomy)

• Removes strip of trabecular meshwork and Schlemm's canal using high-frequency electrocautery 1
• Reduction in IOP and glaucoma medication reported with minimal intraoperative and postoperative complications 1
• Unclear how much pressure reduction is provided by Trabectome versus concurrent cataract extraction, as no randomized studies include phacoemulsification-alone comparison group 1
• Prior laser trabeculoplasty does not significantly affect Trabectome results 1
• Failed Trabectome does not affect success rate of subsequent trabeculectomy 1
• More high-quality studies required to make definitive conclusions 1

Gonioscopy-Assisted Transluminal Trabeculotomy (GATT) and Kahook Dual Blade

• Ab interno goniotomy procedures that remove trabecular meshwork tissue 6, 2
• Most effective when trabecular meshwork dysfunction is primary pathology, not when extensive peripheral anterior synechiae present 6
• Weighted mean IOP reduction of 36.5% for GATT and 25.1% for Kahook Dual Blade in available studies 7
• Favorable safety profile compared to traditional filtration surgery 6

Subconjunctival Drainage MIGS

Xen Gel Stent

• FDA-approved for use in refractory glaucoma 1
• Pivotal single-arm trial demonstrated IOP in mid-teens 1 year after implantation with mitomycin C 1
• Transient postoperative hypotony common, as was requirement for needling 1
• No randomized clinical trials assessing safety and efficacy exist—2018 Cochrane Review found zero RCTs 1
• Selection should be left to treating ophthalmologist's discretion in consultation with patient 1
• Currently no high-quality evidence for effects of subconjunctival draining devices 1

Suprachoroidal MIGS

CyPass Micro-Stent (RECALLED)

• Underwent market withdrawal and FDA Class I recall in 2018 after post-approval study demonstrated significantly greater endothelial cell loss at 5 years versus cataract surgery alone 1
• Was FDA-approved for implantation at time of cataract surgery in mild to moderate POAG before recall 1
• American Society of Cataract and Refractive Surgery recommends monitoring all patients with CyPass for clinically significant corneal edema 1
• In cases of corneal edema caused by device extending into anterior chamber, trimming proximal end recommended rather than repositioning/removal 1

Key Clinical Considerations

General MIGS Characteristics

• All MIGS procedures provide modest IOP reduction with postoperative pressures typically in mid to upper teens—less effective than trabeculectomy and aqueous shunt surgery 1
• More favorable safety profile in short term compared to traditional filtration surgery 1
• Commonly combined with phacoemulsification 1, 4
• Performed using ab interno approach with minimal trauma to ocular tissues 1
• Limited long-term data currently available for all MIGS procedures 1, 4

Critical Preoperative Requirements

• Perform gonioscopy preoperatively, especially when considering trabecular meshwork/Schlemm's canal-based MIGS 1
• Ensure accurate documentation of findings and indications for surgery 1
• Obtain informed consent discussing risks, benefits, alternatives, and expected outcomes 1

Evidence Quality Caveat

• Overall uncertainty regarding effectiveness of MIGS devices for glaucoma, including when used in combination with cataract surgery compared to cataract surgery alone 1
• Most evidence limited to heterogenous nonrandomized studies and uncontrolled retrospective comparisons with few quality randomized control trials 7
• High-certainty evidence exists for IOP reduction benefit in glaucoma, but evidence directly comparing different MIGS treatments is limited 1