Stents and Beyond: Navigating the Waters of MIGS

According to a recent Ocular Surgery News survey, minimally invasive glaucoma surgery (MIGS) is considered the most impactful innovation between 2010 and 2020. With over 3 million Americans with glaucoma, equating to 70 patients for every eyecare provider, any addition to the treatment arsenal is welcome. As revealed in the Eyes On Eyecare 2021 Glaucoma Report, though 80% of optometrists treat glaucoma, ODs only ranked their knowledge of MIGS as 5.97 out of 10.

The Eyes On Eyecare 2022 Glaucoma Report, released after this talk, identifies similar findings with the 83% of optometrists who treat glaucoma registering their knowledge of MIGS at 6.16.

Traditional treatment options, including topical glaucoma drops, drug delivery devices, laser procedures, and intraocular glaucoma surgeries, each have their own set of well documented drawbacks. With topical drops, in addition to complaints of redness and stinging, noncompliance proves to be a major issue. In a study from the University of Michigan’s Kellogg Eye Institute, of 1,000 newly diagnosed, primary open angle glaucoma patients, only 20% claimed compliance at the one-year mark. This number dropped to 15% at 4 years.

Laser trabeculoplasty is often a great first line treatment for patients with glaucoma, however, it's a bridge to the next treatment, not a permanent solution. Though drug delivery devices are an exciting category in emerging glaucoma treatments, the only commercially available and FDA-approved device is labeled as a single-use treatment. However, with additional drug delivery devices coming through clinical trials, there is great promise in this category. With incisional glaucoma surgeries, patients face potentially serious risks, including hypotony.

As glaucoma is a disease that fights back, most patients will need a combination of treatment modalities with MIGS being integral to better outcomes. MIGS, which can also stand for microinvasive glaucoma surgery, utilizes an ab interno approach and microscopic devices with the goal of lowering intraocular pressure by lowering the aqueous flow through different dynamics. These procedures are commonly performed under sublingual anesthesia, which is the same anesthesia that the surgeon uses for cataract surgery.

The majority of MIGS procedures can be done as either stand alone or in conjunction with cataract surgery, giving optometrists an optimal opportunity to refer for MIGS while simultaneously referring for cataract surgery.

MIGS are classified by their mechanism or outflow pathway: trabecular meshwork/Schlemm’s canal (stents, ablation, cutting, dilation), suprachoroidal/supraciliary, subconjunctival, and cyclophotocoagulation (endoscopic transcleral).

For eyecare providers working within the MIGS space, there are two key considerations that come into play with each patient. First, determine the natural state of the crystalline lens, whether phakic or pseudophakic. Next, assess and address the anatomy of the angle preoperatively and perform gonioscopy to ensure an accurate referral.

Within the subtypes listed above, there are 15 options available to surgeons on the market today, each with their pros and cons. These include:

Generally, for maximum safety and quick visual recovery, opt for canal procedures. Viscodilation/Combo procedures provide greater efficacy, but at slightly greater risk. When lowering IOP due a quick progressing glaucoma is priority, transscleral, trab, or tube may prove your best option.

Though there are two products—Cypass and iStent Supra—in the suprachoroidal/supraciliary category, neither is currently available. Due to the incident of endothelial cell loss, Cypass was voluntarily withdrawn from the market by Alcon, and then secondarily removed by the FDA.

Over the past decade, a number of clinical trials and studies have been conducted to determine the efficacy and safety of MIGS using varied baseline IOPs. Overall, MIGS across the board have consistently and significantly lowered IOP with minimal risk in both phakic and pseudophakic individuals.

Follow-up care for MIGS procedures is very similar to cataract surgery. Patients should be seen at one day, one week, one month, and then three months. Potential complications include IOP spikes, inflammation, and bleeding. It is not uncommon to see an immediate IOP spike, which can be remedied by either burping the paracentesis or with topical medications. Inflammation, though common, should be minimal. Far less often, more serious repercussions, such as hyphema, hypotony, endothelial cell loss, and peripheral anterior synechiae can occur.

At some point during the global period, it is imperative to perform gonioscopy to get a view of the device's location and behavior. Using OCT and performing perimetry at the 3 month and 6 month marks, the optometrist can set new baselines for the patient.

With glaucoma coming in as the second leading cause of blindness worldwide and the numbers continuing to grow with the aging population, it is critical for optometrists and ophthalmologists to work closely together to manage this disease.

To this end, research and reach out to surgeons who perform a variety of MIGS to expand your referral network. In your referral, make certain to communicate that you would like to be involved in both the pre-operative and post-operative co-management of the patient. And, most importantly, continue to educate yourself, through talks such as these, on the latest technologies and devices available to ensure the best possible patient outcomes.