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Surgeon: MIGS fills gap between medications, invasive procedures
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CHICAGO – “Our glaucoma drops aren’t that great, and our traditional glaucoma surgery isn’t that great. Enter minimally invasive glaucoma surgery,” John Berdahl, MD, said here at the Optometric Glaucoma Symposium.
The symposium took place just prior to the start of the American Academy of Optometry meeting.
“A hundred percent of the stents I put in are there,” Berdahl said. “Only 50% of the medications I prescribe are taken. We need something better than what we have.”
In addition, “47% of trabeculectomies fail at 3 years, and 30% of tubes fail at 5 years,” he said. “I think of MIGS [minimally invasive glaucoma surgery] as filling this surgical gap between medications and lasers and big hard-core glaucoma surgeries. There has been an explosion in this space.”
Berdahl explained that MIGS performed in the trabecular meshwork is the safest approach, but results in the least amount of IOP lowering. The supraciliary space carries more of a safety risk, but lowers IOP more. Procedures involving the subconjunctival space offer the best IOP lowering potential, but carry the highest risk.
Berdahl said he considers intraocular pressure, family history, optical coherence tomography results, central corneal thickness, optic nerve head, Humphrey visual field and corneal hysteresis in MIGS candidates.
“The biggest things are IOP and Humphrey visual field,” he said. “If the eye pressure is high, there’s room for me to get it down. If the pressure is already low, then some of the trabecular bypass devices won’t work. If they’re just hanging on by an axon with their visual field, we don’t have time to see if a safer procedure will help and have to move on to a tube shunt or trabeculectomy.”
Berdahl and colleagues conducted a retrospective study on 464 of their patients who were implanted with the iStent (Glaukos). The preoperative IOP with the patients on medication was 19.2 mm Hg, and in 108 patients followed at 3 years, it was 14.8 mm Hg.
“We get about 4 mm Hg to 4.5 mm Hg of IOP lowering when you combine cataract surgery and an iStent,” Berdahl said. “We also get about a 30% to 50% reduction in medications. The iStent doesn’t work as well on patients with low IOP.
“With those starting at 14 mm Hg, it lowers it about 1 mm Hg,” he continued. “Starting at 18 mm Hg, it lowers about 2.5 mm Hg. But once IOP gets higher, 22 mm Hg to 26 mm Hg, you get 6.5 mm Hg lowering. If it’s 27 mm Hg or more you get 12 mm Hg more lowering than with an IOP drop.”
Berdahl said he and his colleagues also studied the iStent and pseudophakia.
“Preop IOP was 20 mm Hg or 20.5 mm Hg,” he said. “On average, they were taking 2.2 medications. In a 24-month time period, the pressure came down to 13 mm Hg, on average, and the medications dropped about 30%. We know that iStent in pseudophakes lowers IOP as well.”
Berdahl said his group just completed a study of the Kahook Dual Blade (New World Medical). He said the preoperative IOP was 17.5 mm Hg, and the postoperative IOP was 13 mm Hg. The medication usage went from 1.7 to 1.1.
“We don’t know how long this will last, but it looks like there will be some sustained IOP lowering effect,” he added.
The Cypass (Alcon) is performed in the suprachoroidal space with cataract surgery and has been shown to lower IOP by 7 mm Hg compared to 5.3 mm Hg with cataract surgery alone, Berdahl said.
“The percentage of patients medication-free after Cypass was considerably higher,” he said.
The Xen gel stent (Allergan) has been shown to lower high pressures to 15.9 mm Hg in refractory glaucoma patients, Berdahl added.
Berdahl explained that cataract surgeons may wonder if they have enough patients with both cataract and glaucoma to justify an investment in MIGS procedures. He said that several studies have shown that 20% of patients undergoing cataract surgery have a concurrent diagnosis of glaucoma.
“The average cataract surgeon in the U.S. does 400 cataracts a year,” he said. “That means they would be doing 40 to 80 patients that have both glaucoma and cataract. If you’re doing a reasonable number of cataracts per year, you’ll see enough glaucoma to become decent in MIGS.”
Berdahl said it’s incumbent upon clinicians to explain all of the options to patients.
He said ideal candidates for MIGS include those with cataract and glaucoma or ocular hypertension, pseudophakic patients with uncontrolled glaucoma and occasional phakic patients with uncontrolled glaucoma.
“MIGS fills a huge void,” Berdahl concluded. “It’s safe, effective, doable, well covered and fairly reimbursed, for the most part.” – by Nancy Hemphill, ELS, FAAO
Reference:
Berdahl J. Minimally invasive glaucoma surgery. Presented at: Optometric Glaucoma Society annual meeting; Chicago; Oct. 10, 2017.
Disclosures: Berdahl reports he has relationships with Alcon, Allergan, AMO, Avedro, Aurea Medical, Bausch + Lomb, Calhoun, Clarvista, Dakota Lions Eye Bank, Digisight, Envisia, Equinox, Glaukos, Imprimis, Iantech, New World Medical, Ocular Therapeutix, Omega Ophthalmic, Ocular Surgical Data, Sightlight Surgical, Vittamed, Vance Thompson Vision and Veracity.