MIGS

Glaucoma is often referred to as the “silent thief of sight.” Characterized by progressive damage to the optic nerve—frequently driven by elevated intraocular pressure (IOP)—it stands as one of the leading causes of irreversible blindness worldwide. For decades, ophthalmologists managed glaucoma through a rigid sequence: starting with prescription eye drops, proceeding to laser therapy, and resorting to traditional, invasive surgeries like trabeculectomy or tube shunt implantation when conventional options failed.

While traditional surgeries effectively lower intraocular pressure, they carry significant risks of severe complications, prolonged recovery times, and frequent follow-up visits. In recent years, an innovative class of surgical interventions has fundamentally reshaped the treatment paradigm: Micro-Invasive Glaucoma Surgery (MIGS).

Offering a safer, less traumatic alternative, MIGS bridges the gap between medication management and major invasive surgery, revolutionizing modern ophthalmic care.

What is MIGS?

Micro-Invasive Glaucoma Surgery (MIGS) refers to a group of surgical techniques and tiny implantable devices designed to lower intraocular pressure with minimal tissue disruption. First popularized in the early 2010s, MIGS procedures utilize microscopic equipment, microscopic incisions, and high safety profiles to enhance the eye’s natural drainage system.

To be classified as a true MIGS procedure, an intervention generally satisfies five core criteria:

Micro-Incision: Performed through tiny, self-sealing clear corneal incisions that preserve surrounding tissue.
Minimal Tissue Trauma: Avoids extensive cutting or disruption of the conjunctiva and sclera.
Efficacy: Demonstrates consistent lowering of intraocular pressure and reduces reliance on glaucoma medications.
High Safety Profile: Exhibits significantly fewer severe complications compared to traditional filtering surgeries (such as hypotony, bleb infections, or hemorrhages).
Rapid Recovery: Facilitates fast visual recovery with minimal postoperative discomfort.

How MIGS Works: Pathways to Lower Intraocular Pressure

In a healthy eye, fluid called aqueous humor is continuously produced in the ciliary body and drains out through two primary pathways: the trabecular meshwork (conventional route) and the uveoscleral pathway (unconventional route). In glaucoma, resistance within these outflow pathways causes fluid to build up, elevating intraocular pressure and damaging the fragile optic nerve fibers.

MIGS procedures lower intraocular pressure by restoring or bypassing these compromised drainage channels.

                  [ Ciliary Body Produces Aqueous Humor ]
                                    │
                                    ▼
                     [ Fluid Accumulates in Eye ]
                                    │
                                    ▼
       ┌────────────────────────────┼────────────────────────────┐
       ▼                            ▼                            ▼
[ Trabecular Meshwork ]    [ Suprachoroidal Space ]    [ Subconjunctival Space ]
 (iStent, Hydrus, Kahook)        (CyPass, iStent)           (XEN, PreserFlo)
       │                            │                            │
       └────────────────────────────┼────────────────────────────┘
                                    │
                                    ▼
                [ Restored Outflow & Reduced IOP ]

Key Categories of MIGS Procedures

MIGS devices and approaches target specific anatomical pathways within the eye, classified into four main surgical categories:

MIGS Category	How It Works	Common Devices / Procedures	Primary Indications
Micro-Stents (Trabecular Outflow)	Tiny titanium or nitinol implants placed into the trabecular meshwork to bypass fluid resistance directly into Schlemm’s canal.	iStent inject, Hydrus Microstent	Mild-to-moderate open-angle glaucoma; often combined with cataract surgery.
Tissue Excision & Canaloplasty	Clears, opens, or strips away blocking tissue in the trabecular meshwork using specialized blades, catheters, or goniotomy tools.	Kahook Dual Blade (KDB), OMNI Surgical System, GATT	Mild-to-severe open-angle glaucoma; standalone or combined with cataract surgery.
Subconjunctival Shunts	Creates a micro-channel directing fluid from the anterior chamber to a small reservoir under the conjunctiva (similar to a miniature trabeculectomy).	XEN Gel Stent, PreserFlo MicroShunt	Moderate-to-severe refractory glaucoma where conventional pathways are damaged.
Cyclophotocoagulation (Ciliary Body)	Uses targeted laser energy (microsecond transscleral cyclophotocoagulation) to reduce aqueous humor production at the source.	MicroPulse Transscleral Laser Therapy	Refractory or advanced glaucoma; non-incisional outpatient treatment.

Benefits of Combined Cataract and MIGS Surgery

One of the greatest clinical advantages of MIGS is its seamless compatibility with cataract surgery. Because both open-angle glaucoma and cataracts predominantly affect older adults, many patients suffer from both conditions simultaneously.

During routine cataract surgery (phacoemulsification), the surgeon makes a micro-incision in the cornea to replace the cloudy natural lens with a clear intraocular lens (IOL). Through that exact same tiny incision, the surgeon can implant a MIGS device or perform a micro-goniotomy in just a few additional minutes.

Key Advantages of Combined Procedures:

Single Surgical Session: Patients address both vision loss from cataracts and elevated eye pressure in one operation.
Synergistic Pressure Reduction: Cataract removal alone offers modest reductions in intraocular pressure; adding a MIGS device enhances pressure control substantially.
Reduced Medication Burden: Many patients are able to reduce or eliminate their daily glaucoma eye drops, alleviating common side effects like chronic dry eye, ocular redness, and financial strain.

Limitations and Future Directions

While MIGS has revolutionized glaucoma care, it is not a universal substitute for all glaucoma surgeries.

For patients with advanced, end-stage glaucoma requiring extremely low target intraocular pressures (e.g., single-digit IOPs), traditional filtering surgeries like trabeculectomy remain the clinical gold standard. Additionally, certain types of angle-closure glaucoma or severe anatomical scarring may limit the feasibility of specific trabecular MIGS devices.

Looking ahead, ongoing innovations in drug delivery and biomaterials promise to refine MIGS even further. Sustained-release intraocular drug implants (such as bimatoprost implants) and next-generation bio-compatible materials continue to expand the scope of minimally invasive surgical options.

Conclusion

Micro-Invasive Glaucoma Surgery represents a landmark shift in ophthalmic medicine. By providing an effective, gentle, and highly versatile middle ground between daily eye drops and aggressive traditional surgery, MIGS empowers clinicians to intervene earlier and protect visual fields. As device technology and clinical research continue to advance, MIGS will remain a cornerstone in preserving sight and improving the overall quality of life for millions living with glaucoma.