Expert panel provides consensus recommendations on use of PreserFlo microshunt device
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A panel of expert glaucoma surgeons reached consensus on patient selection and preoperative, perioperative and postoperative management with the PreserFlo microshunt drainage device.
“The information we gathered will provide guidance for surgeons who want to introduce this tool in their practice,” lead author Anthony P. Khawaja, MD, PhD, told Healio/OSN.
The microshunt has been available in Europe since 2019, and a good number of surgeons, geographically spread across Europe, have gathered experience with at least 100 cases. Most of them are also familiar with other drainage devices.
“We invited 12 of them to take part in a three-round modified Delphi panel,” Khawaja said.
The device
The PreserFlo microshunt (PMS, Santen) is a minimally invasive glaucoma surgical device that drains the aqueous humor to the subconjunctival space. It is designed to be implanted ab externo, which is different from the Xen gel stent (Allergan).
“You open the conjunctiva and the Tenon’s and make a pocket through which the microshunt is inserted. There are two small wings within it, positioned 4.5 mm from the tip, that help secure the device in place,” Khawaja said.
The length of the device, 8.5 mm, is also an advantage because it promotes a more posterior flow, and the bleb is far back.
“These flatter and more posterior blebs are great and more amenable to contact lens wear as compared with trabeculectomy or Xen blebs,” Khawaja said.
The material is a synthetic polymer known as SIBS, first used in coronary stents. It is a highly biocompatible and inert material that minimizes foreign body reaction and is resistant to degradation.
Patient selection
All panelists were involved in three consecutive Delphi rounds between September and December 2021. Consensus was set at a predefined threshold of at least 70% of panelists. Full consensus was achieved on the use of the PreserFlo to lower IOP in patients with primary open-angle glaucoma, specifically with IOP greater than 21 mm Hg.
“We all agreed that it is useful for people who don’t have good enough IOP control despite maximum medical therapy, people who have problems with adherence or tolerance to treatment, and patients who have progressive visual field loss,” Khawaja said.
In addition, panelists agreed that the device might be useful in patients with other forms of glaucoma, including pseudoexfoliation and pigment dispersion. They also agreed that it is suitable for patients with high myopia, which is typically a relative contraindication for trabeculectomy due to the risk for hypotony.
“Then, unsurprisingly, we all agreed that it should not be used in neovascular glaucoma, but there wasn’t consensus, and we remained uncertain about uveitic glaucoma and normal-tension glaucoma,” Khawaja said. “We also stated that patients should ideally not have had incisional glaucoma surgery or cataract surgery within the last 6 months because this may cause a strong healing response and possibly failure of the surgery.”
Surgical procedure
Perioperative considerations included the use of mitomycin C, in an area as wide as for trabeculectomy, to reduce the risk for subconjunctival fibrosis and increase the chance of surgical success.
“Something interesting for me was that when I first learnt, I was always implanting the PMS at 12 o’clock, and now there’s a strong consensus that you should go slightly to one side or the other, at 11 or 1 o’clock, to avoid the superior rectus muscle. Also, I put a little stitch to prevent the device from sticking up and getting caught at Tenon’s, but there was no agreement on that, and a lot of people are still unsure about whether that’s a good idea,” Khawaja said.
Everyone agreed that the procedure is quick to learn for surgeons who are used to performing trabeculectomy.
“You only need to do a few cases, and you’ll already be very good at it, which might not be the case for some other procedures,” Khawaja said.
Postoperative management
The majority of panelists agreed that the follow-up period is more predictable as compared with trabeculectomy and that, on average, patients need fewer visits. Despite the cumulatively high volume of surgeries, no case of corneal endothelial decompensation was reported.
“We believe that, if that is a side effect, it is uncommon,” Khawaja said.
In case the microshunt fails, most surgeons felt that they would go for trabeculectomy.
“This is not something I would personally do. I would probably go straight to a full-size aqueous shunt. This is an area where we look forward to more studies in the future to see how successful a trabeculectomy is after a PMS. Maybe then I’ll change my mind,” Khawaja said.
He looks forward to further studies also to clarify whether the PreserFlo may have a role in normal-tension glaucoma, when IOP is in the high teens.
“And in terms of the surgical technique, it will evolve, as surgical techniques always do. So, I think we are going to delve deeper into this with a further consensus panel in the near future,” he said.
For more information:
Anthony P. Khawaja, MD, PhD, can be reached at email: anthony.khawaja@ucl.ac.uk.
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