MIGS brings balance to combined cataract-glaucoma surgery

By Cheryl Guttman Krader

The need for cataract surgery has often been the tipping point for proceeding with surgical management of glaucoma, but in 2015, surgeons are better able to tailor their intervention based on where the patient lies along the spectrum of glaucoma.

“After the drug renaissance of the late 1990s and early 2000s, combined cataract surgery with a filtering or tube procedure began to be reserved for glaucoma patients at high risk for functional impairment,” said Thomas W. Samuelson, MD, adjunct associate professor of ophthalmology, University of Minnesota, Minneapolis, and attending surgeon, Minnesota Eye Consultants, Minneapolis. “Today, combined surgery is performed in a broader population thanks to the availability of alternatives that are far less likely to cause iatrogenic vision loss.”

Watch as Thomas Samuelson, MD, outlines how he manages patients with cataracts and glaucoma.

Dr. Samuelson said that while cataract surgery is not a cure for glaucoma, it is an important management option that can result in significant IOP reduction. Therefore, he considers phacoemulsification alone useful for patients needing cataract surgery who have untreated ocular hypertension or are glaucoma suspects.

Patients with mild-to-moderate glaucoma are candidates for phacoemulsification plus “enhanced microinvasive glaucoma surgery (MIGS),” which would involve ab interno trabeculectomy (Trabectome, NeoMedix), a trabecular microbypass stent (iStent, Glaukos), or endoscopic cyclophotocoagulation plus some postoperative medication.

Trabeculectomy or a tube procedure remains an important option to combine with phacoemulsification for patients who need cataract surgery and are at high risk for functional impairment (patients with severe glaucoma, poor compliance, extreme IOP, medication intolerance, or aggressive progression).

Enhanced MIGS

Explaining the rationale for enhanced MIGS, Dr. Samuelson said that while highly safe, the current MIGS options have modest efficacy. Use of one or two topical medications after MIGS provides patients with additional IOP-lowering effect in, what Dr. Samuelson terms, “minimally intrusive sustainable therapy (MIST).” Continued use of medication in this manner should not be viewed as surgery failure, he added.

“The ability of a surgical procedure to completely eliminate medications is a laudable goal, but does not have to be achieved to consider the procedure a success,” Dr. Samuelson explained. “It is a fact that we have superb glaucoma drugs, but it is also a fact that we are overusing them in some patients and that ocular surface toxicity is rampant. With MIGS we can successfully convert patients from an unrealistic, unsustainable medication schedule to a reasonable regimen of just one or two drops per day, a regimen that is minimally intrusive, and sustainable.”

He added that in the future, the introduction of sustained, delivery-drug systems might take MIGS with MIST to the next level.

Gearing up for MIGS

Dr. Samuelson noted that while it may be unrealistic for surgeons to adopt all MIGS procedures, they should pick one so that they will be able to offer an alternative to trabeculectomy or tube procedures. Dr. Samuelson said he chose the trabecular microbypass stent, and he offered a few tips for success.

First, Dr. Samuelson advised surgeons to master intraoperative gonioscopy–since excellent visualization is critical to achieve accurate placement of the device. When implanting the stent, he recommended approaching the trabecular meshwork at a slight angle and to be definitive when penetrating the trabecular meshwork.

“You want to be steep enough with your line of attack so that you will get to the back wall of the canal, and use enough force to push the stent through the juxtacanalicular meshwork,” Dr. Samuelson pointed out. “Being too superficial with stent placement was the most common error I made in my early cases.”

Once the device is in Schlemms canal, the insertion is completed by flattening the angulation, dropping the heal or lifting the toe of the device, while maintaining full visualization the entire time.

Dr. Samuelson said the reflux of blood when the stent first enters Schlemms canal is a nice sign that the stent is properly placed. However, blood reflux does not always occur or it may not be seen until all of the viscoelastic is removed from the eye. Blood coming out through the snorkel following placement is a tell-tale sign the device is communicating with the episcleral vasculature, but it will only be visualized when the eye is soft and below episcleral venous pressure.

Dr. Samuelson also suggested that continuous medical therapy after MIGS should be established with patients during a preoperative discussion. That approach will avoid the frustration of the patient to ask in the recovery room, “What should I do with my glaucoma medications?”

“Better to make the immediate postop medication decisions preoperatively so the patient knows which glaucoma medications to stop and which to continue after surgery,” Dr. Samuelson said. “This avoids somewhat arbitrary, on-the-fly, glaucoma medication decisions in the recovery room.”