Minimally Invasive Glaucoma Surgery (MIGS): An Overview

Risantini Murugan

Introduction

Glaucoma is a chronic eye condition in which impaired drainage of aqueous humour leads to elevated intraocular pressure (IOP) and progressive optic nerve damage. Traditionally, it has been managed with medications, laser therapy, or invasive surgeries such as trabeculectomy and aqueous shunt implantation. Minimally Invasive Glaucoma Surgery (MIGS) encompasses a range of less invasive procedures that target the trabecular meshwork, suprachoroidal space or Schlemm’s canal, designed to bridge the gap between medications, laser therapy, and conventional surgery. While MIGS is relatively new, having been in clinical use for just over a decade, it has rapidly evolved and gained acceptance among glaucoma specialists (1). Importantly, MIGS is often performed alongside cataract surgery, which can enhance the pressure-lowering effect of cataract extraction itself.

What is MIGS?

The aqueous humour is produced by the ciliary body epithelium and flows from the posterior chamber through the pupil into the anterior chamber. Most of this fluid (approximately 75%) drains through the trabecular meshwork into Schlemm’s canal, while the remainder exits via the uveoscleral pathway (2). MIGS procedures were developed to enhance natural aqueous outflow or create alternative drainage routes, providing a safer and less invasive way to reduce intraocular pressure.

MIGS excludes devices such as Xen Gel Stent or Preserflo Microshunt, since these involve the formation of a bleb. Performing MIGS requires familiarity with gonioscopy: the gonio lens must be held in the non-dominant hand, the operating microscope needs to be tilted, and the patient’s head rotated away from the surgeon to allow optimal visualisation of the angle and trabecular meshwork. The main MIGS procedures can be grouped by their anatomical target (3,4):

Trabecular meshwork bypass

  • Hydrus– miniature implants (8 mm in length and 290 microns in diameter) inserted into Schlemm’s canal to scaffold the drainage pathway and improve fluid outflow. The main limitation is that it requires an additional incision, unlike most other MIGS, which can be performed through the standard cataract surgery incisions.
  • iStent inject/ iStent infinite – the smallest implantable device in the human body. Using a handheld injector, surgeons can deploy two (iStent inject) or three (iStent infinite) titanium stents, which allow direct aqueous flow from the anterior chamber into Schlemm’s canal.
  • Elios – performed via a minimal corneal incision using a high-precision, non-thermal laser to create 10 microchannels through the trabecular meshwork, thereby enhancing aqueous humour outflow.
  • Trabectome– uses an electrical pulse to remove a portion of the trabecular meshwork, thereby reducing resistance to aqueous humour outflow.
  • Kahook dual blade – similar in principle to the Trabectome but without the electrical pulse or in-built irrigation. The specially designed blade excises a strip of trabecular meshwork, enhancing outflow.

Schlemm’s canal-based approach

  • iTrack – a microcatheter is inserted into Schlemm’s canal and advanced 360° to open stenotic segments. As the catheter is withdrawn, viscoelastic material is deposited in each quadrant to expand the drainage channels. A unique feature is the iTrack’s red flashing beacon, which allows real-time visualisation of catheter position, unlike the Omni device, which is advanced without direct visual guidance.
  • Omni – an implant-free device that, like iTrack, uses viscodilation to expand Schlemm’s canal and collector channels, but it also permits trabeculotomy in addition to canaloplasty.

Ciliary body/ Supraciliary space devices

  • Endocyclophotocoagulation (ECP) – a laser probe is advanced across the anterior chamber to target the ciliary body from apex to base, permanently ablating ciliary processes and reducing aqueous humour production. This is the only MIGS procedure that decreases aqueous production, whereas all others enhance aqueous outflow.
  • MINIject – is a soft, flexible implant made of porous material, inserted between the scleral spur and ciliary body to enhance aqueous humour outflow through the supraciliary space.

Conclusion

MIGS represents an innovative shift in glaucoma management, providing safer and less invasive alternatives to traditional surgery (1). While it effectively lowers intraocular pressure, reductions are often modest and may not be sufficient for advanced glaucoma (1). Outcomes can be highly variable, depending on the device used and surgical technique (5). As such, further research is needed to assess the long-term efficacy and durability of different MIGS procedures. With continued innovation, robust evidence, and specialised surgical training, MIGS has the potential to become a mainstay, or even a first-line intervention in glaucoma care.

References

  1. Singh IP, et al. Clinical outcomes and patient-reported outcomes of MIGS techniques: a systematic review 2014–2025. Curr Opin Ophthalmol. 2025. [PMID: 40809659]
  2. Goel, M. (2010). Aqueous Humor Dynamics: A Review. Open Ophthalmology Journal, 4, 52-59.
  3. Glaucoma UK. (n.d.). MIGS (Minimally Invasive Glaucoma Surgery). Retrieved September 20, 2025, from https://glaucoma.uk/about-glaucoma/treatments-surgery/migs.
  4. Microinvasive Glaucoma Surgery (MIGS). EyeWiki. Accessed [1st October 2025]. URL: https://eyewiki.org/Microinvasive_Glaucoma_Surgery_(MIGS)
  5. Ansari E, et al. Building consensus on MIGS: results from the UK Eye Glaucoma Society survey. Eye (Lond). 2025. [DOI: 10.1038/s41433-025-03852-9].

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