MINIMALLY INVASIVE GLAUCOMA SURGERY

MINIMALLY INVASIVE GLAUCOMA SURGERY

November 24, 2021

Glaucoma is a disease where the optic nerve gets damaged and the main risk factor is elevated eye pressure (also called intraocular pressure, IOP). The only treatment is to lower the IOP.

We often think of the inside of the eye like a drain and a faucet, and using this analogy, high IOP is related to an imbalance between the amount of fluid made inside the eye and the amount of fluid the eye can drain.

This fluid is called the aqueous and when we consider various treatment options to lower IOP, we can either decrease the amount of aqueous the eye makes or increase the drainage of aqueous from inside the eye. This goal can be accomplished with medications, laser, or surgery.

The traditional glaucoma surgeries (trabeculectomy and glaucoma drainage devices), while very effective, are associated with risks such as double vision, devastating eye infections, exposure of a drainage implant, swelling of the cornea, and excessively low IOP. 

Although these risks are relatively infrequent, they make most surgeons delay glaucoma surgery until all other less invasive treatment options are maximized (medications and laser treatment) and the patient has definitive glaucoma worsening.

Over the past 5-10 years there has been a revolution in glaucoma surgery, specifically Micro-Invasive Glaucoma Surgery, commonly called MIGS.

The Last 25 Years

Of all the subspecialties in ophthalmology, it could be said that glaucoma has seen the most disruptive change over the last 25 years. Glaucoma has shifted from a disease treated primarily with pharmaceuticals to a disease treated surgically.

It is the MIGS — for minimally invasive glaucoma surgery — revolution that has initiated this change. In 1992, Martin Uram, MD, MPH, developed endoscopic cyclophotocoagulation (ECP) and it became adopted by general ophthalmologists, glaucoma specialists and even retinal specialists around the world to treat glaucoma at the time of cataract surgery or for refractory glaucoma.

In many ways, ECP was the first MIGS procedure because it was bleb-free and could be used to treat all stages of glaucoma and multiple types of glaucoma, including angle-closure glaucoma.

Then in the early 2000s, George Baerveldt, MD, developed the Trabectome procedure (MST), which was used to remove a strip of trabecular meshwork (TM) with a bipolar electrode under direct gonioscopic view.

The first Trabectome procedure in the United States was in 2006. The 2010s were, in many ways, the decade of MIGS. In 2012, the FDA approved the iStent (Glaukos) to bypass the TM, followed by the iStent inject and the Hydrus implant (Ivantis) in 2018.

The last decade also saw the increase in ab interno canaloplasty and goniotomy with a variety of devices, such as the OMNI Surgical System (Sight Sciences) and its predicate devices the TRAB360 and VISCO360, the Kahook Dual Blade (New World Medical) and the Trab-Ex goniotomy system (MST).

Also, we saw the resurrection of the iTrack microcatheter, a device intended for ab externo canaloplasty, and repurposed as an ab interno technique to perform 360° of canal viscodilation.

In addition, Allergan released the XEN Gel Stent. Although not a true MIGS procedure because it is bleb-forming, it is certainly a less-invasive procedure, especially with clinically significant hypotony being truly rare.

Other new surgical MIGS devices are currently in clinical trials. Combined with the advent of sustained-release implant of drugs, these should lead to the full manifestation of the interventional glaucoma revolution and the potential for the near-cessation of eyedrops to treat glaucoma.

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