Take-home: A new trabecular meshwork excision blade takes a new approach in IOP reduction.
AURORA, COLORADO—A new trabecular meshwork excision blade is yet another option for glaucoma surgeons in their quest to lower patients’ IOP.
The dual blade (Kahook Dual Blade, New World Medical) is engineered for angle anatomy and incises the trabecular meshwork through paired incisions to allow for tissue removal, said Leonard K. Seibold, MD, assistant professor and codirector, Glaucoma Fellowship, University of Colorado School of Medicine.
Use of the blade can be paired with cataract surgery or as a standalone procedure. The blade is one of several new minimally invasive surgery options within glaucoma.
“The dual blade performs a goniotomy through the trabecular meshwork to allow increased aqueous outflow, thereby lowering IOP,” Dr. Seibold said.
Four unique design features of the blade, according to Dr. Seibold, include its sharp tip, which can pierce through the trabecular meshwork; a ramp that elevates and stretches the trabecular meshwork; a dual blade that helps to incise and results in a free strip of meshwork; and a footplate that fits atraumatically in Schlemm’s canal.
The single-use, disposable blade is used via an ab interno approach through a clear corneal incision. It is placed in the anterior chamber and the tip of the blade is pierced across the trabecular meshwork, then the dual blades create two incisions as the blade is advanced, Dr. Seibold said. A free strip of trabecular meshwork is created and removed. Surgeons can treat approximately 90 to 150 degrees of the angle.
If use of the dual blade is combined with cataract surgery, the post-op regimen is similar to that of standard cataract surgery. Patients use a nonsteroidal inflammatory drug and a topical steroid tapered over three to four weeks. Pilocarpine is added to keep the cleft open for four weeks; patients restart their glaucoma drops as needed.
Clinical data from eight surgeons and 122 patients who mostly had moderate or severe open-angle glaucoma revealed that in 93% of cases, trabecular meshwork was removed from the anterior chamber, Dr. Seibold said.
The average extent of removal was 114 degrees; in 98% of cases, surgeons said that use of the blade was easy and straightforward.
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An analysis of post-op outcomes at three months found a 33% reduction in IOP, from 17.5 mm Hg pre-op to 11.8 mm Hg post-op. Sixty-nine percent of patients were able to stop using at least one of their glaucoma medications after surgery.
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The strip of free tissue that is removed with the blade offers potential for future analysis, which researchers at the University of Colorado are currently considering. “We’ve never been able to take live trabecular meshwork samples of this size in glaucoma patients and study them. We can look for ultrastructural changes that may give us insight into its pathogenesis. There is also the potential for genetic analysis. We’re just on the cusp of diving in to see where this opportunity will lead us,” Dr. Seibold said.
Looking at adverse events, about 40% of patients experienced hyphema intra-operatively, but that percentage dwindled to 9% at post-op day one. That percentage is more favorable compared with other trabecular meshwork-focused procedures, Dr. Seibold said. One patient needed additional surgery for uncontrolled IOP.
Although other IOP-lowering procedures are also effective, Dr. Seibold said that use of the Kahook blade is the only one that can bypass the trabecular meshwork without an implant, has no moving parts or additional equipment to acquire, and leaves no large remnants of trabecular meshwork behind. Still, head-to-head trials and longer-term outcomes are needed, he added.
Leonard K. Seibold, MD
This article was adapted from Dr. Seibold’s presentation at the 2016 meeting of the American Society of Cataract and Refractive Surgery. Dr. Seibold is a consultant for New World Medical.