Table of Contents
Introduction
Glaucoma is a long-term eye condition that damages the optic nerve and leads to permanent vision loss, often without early symptoms. Traditional treatments include eye drops and laser procedures to lower eye pressure, but surgery is needed for severe cases, which comes with risks and long recovery times. Minimally Invasive Glaucoma Surgery (MIGS) offers a newer option for patients with mild-to-moderate glaucoma who struggle with eye drops. MIGS can be done during cataract surgery, reducing dependence on medication and involving fewer complications.
What Is the Difference Between MIGS vs Trabeculectomy?
MIGS:
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MIGS includes a variety of new procedures designed to treat glaucoma with minimal tissue manipulation compared to traditional surgeries like trabeculectomy or tube-shunt surgery.
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MIGS involves less manipulation of eye tissues, causing less trauma to the eye.
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These procedures are generally faster to perform and have a quicker recovery time.
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MIGS is considered safer but may not always lower eye pressure as effectively as traditional surgeries.
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Since MIGS is relatively new, long-term results are still being studied.
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MIGS is usually recommended for less severe glaucoma cases, often performed along with cataract surgery.
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Different MIGS devices work in various ways and come with their risks and benefits, which can be confusing.
Trabeculectomy:
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Trabeculectomy remains the gold standard for glaucoma surgery.
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Trabeculectomy has a long track record of effectively lowering eye pressure.
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It is the preferred procedure for advanced glaucoma, normal tension glaucoma, or eyes with narrow drainage angles.
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MIGS devices are unsuitable for eyes with narrow angles and are not recommended when very low eye pressure is needed.
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Some secondary glaucoma types are better treated with tube-shunt surgeries.
Comparing MIGS and Trabeculectomy:
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Traditionally, glaucoma was mostly treated with medications, and surgery was only for severe cases. Now, with MIGS, surgery can be considered earlier in the disease.
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Often, the choice is between MIGS and eye drops rather than MIGS and trabeculectomy. Trabeculectomy is still mainly for more advanced glaucoma cases.
What Are the Types of Minimally Invasive Glaucoma Surgery (MIGS)?
Trabecular Meshwork Bypass
The trabecular meshwork (TM) is the main area where resistance to the drainage of eye fluid (aqueous humor) occurs, which can lead to high intraocular pressure (IOP). Minimally Invasive Glaucoma Surgery (MIGS) techniques can help by removing or bypassing this tissue, allowing fluid to flow directly into the Schlemm's canal and reducing IOP. This is particularly useful for conditions like primary open-angle glaucoma (POAG), pigmentary glaucoma, and ocular hypertension, aiming to achieve a target IOP of 15 to 16 mm Hg (millimeter of mercury). However, it is unsuitable for angle-closure glaucoma (PACG), neovascular glaucoma (NVG), corneal opacity, and certain other conditions.
Stents
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iStent: The first FDA-approved MIGS device (2012), made of titanium and coated with heparin. It is tiny (one millimeter (mm) x 0.3 mm) with a central opening for fluid to pass through. Inserted through a small corneal incision using a special tool. It reduces IOP by about 25 percent in most patients and significantly reduces the need for medications.
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iStent Inject: A second-generation device (approved in 2018), also titanium and heparin-coated, but slightly different in design comes with two stents pre-loaded in an injector for easier placement. It can reduce IOP by 35 to 39 percent, and many patients become medication-free within a year.
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Hydrus Stent: A crescent-shaped, eight-millimeter-long stent made of nitinol, which expands in the Schlemm's canal implanted through a small corneal incision reduces IOP by more than 20 percent in most patients, and many become medication-free.
Tissue Excision (Trabeculectomy) - Bypassing the TM
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Kahook Dual Blade (KDB) Goniotomy: A blade with two edges designed to cut and remove a section of the TM performed through a small corneal incision using a gonioscope reduces IOP by about 20 percent in most patients with minimal tissue damage.
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Trabectome: A device that uses plasma energy to remove a portion of the TM inserted through a small incision. It reduces IOP by about 40 percent and is effective even in difficult cases like narrow-angle glaucoma.
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Laser Trabeculectomy: Laser energy creates small channels in the TM. It is performed with a laser fiber and visualized with a gonioscope. It reduces IOP by 20 to 40 percent.
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Gonioscopy-Assisted Transluminal Trabeculotomy (GATT): A microcatheter is used to cut through the TM, and the procedure is performed with a gonioscopy to guide the catheter. It reduces IOP by 30 to 40 percent and is particularly useful for congenital and juvenile glaucoma.
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Ab Interno Canaloplasty (AbiC): Uses a microcatheter to dilate the Schlemm's canal performed through a small incision and reduces IOP by 30 to 40 percent.
Suprachoroidal Shunts:
These devices help drain fluid into the suprachoroidal space (between the eye's outer layers), increasing fluid outflow.
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Cypass Stent: A flexible, fenestrated stent initially used for glaucoma but withdrawn due to high endothelial cell loss.
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iStent Supra: A curved tube that facilitates fluid outflow reduces IOP by 20 percent when combined with medication.
Subconjunctival Filtration Stents:
These implants create a new drainage pathway for eye fluid to reduce IOP.
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Xen Implant (Xen Gel Stent): Made of gelatin, this tube creates a new drainage route into the subconjunctival space. It is inserted through a small incision and reduces IOP by 29 to 41 percent in many patients.
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InnFocus MicroShunt (PRESERFLO MicroShunt): A small tube made from a special material (SIBS) that drains fluid to reduce IOP. Surgically implanted with specific preparation steps. Shows long-term IOP control in most patients.
Endocyclophotocoagulation (ECP):
This technique reduces fluid production by ablating parts of the ciliary body with a laser. It is used in various glaucoma types, including pediatric cases. It is performed using a probe with a laser inserted through a small incision. In combination with other treatments, it reduces IOP by about 35 percent.
These MIGS techniques provide various options for managing glaucoma by reducing intraocular pressure, improving fluid outflow, and reducing medication dependency. Each technique has specific indications, effectiveness, and potential complications.
What Is the Recovery Time for MIGS?
The recovery time for minimally invasive glaucoma surgery is much shorter than for traditional procedures. A person can get back to work and their usual activities quickly. Follow-up appointments will be needed to monitor the eye pressure to heal. Full recovery typically takes about one to four weeks, whereas traditional surgery can take two to three months.
Conclusion
Microinvasive glaucoma surgery (MIGS) has greatly improved treatment for patients with mild to moderate glaucoma. As surgeons gain more experience and MIGS techniques expand, these procedures may also be used for more severe cases. MIGS is particularly beneficial for patients who cannot tolerate medications, do not stick to their treatment plan, or need more eye pressure reduction than drops or lasers can provide. MIGS can be easily added to routine cataract surgery and is an option for patients who want to stop using eye drops. The field of MIGS has grown quickly in the past decade, giving glaucoma surgeons more options to customize treatment for each patient. New devices and techniques will continue to emerge in the future.
