Study shows positive safety, efficacy outcomes of Xen45 gel stent in short term
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The Xen45 gel stent showed promising short-term safety and efficacy in patients with refractory glaucoma, according to a poster presented at the virtual Association for Research in Vision and Ophthalmology meeting.
“Decreased efficacy at 6 months may be due to the smaller sample size available at that time point,” Alexander B. Crane said.
The Xen gel stent (Allergan) consists of a 6-mm hydrophilic tube made of collagen-derived gelatin cross-linked with glutaraldehyde, is non-inflammatory and is theorized to cause minimal tissue response. It is injected in the subconjunctival space, tunneling through a scleral channel and ending in the anterior chamber.
“It decreases IOP by creating a permanent drainage shunt from the anterior chamber to the subconjunctival space, taking advantage of the principles of laminar fluid dynamics, specifically the Hagen-Poiseuille equation, to prevent hypotony. With this equation, it can be calculated that at an average aqueous humor production of 1 µL/min to 2 µL/min, the 6-mm long tube with an internal lumen diameter of 45 µm provides a steady-state pressure of approximately 6 mm Hg to 8 mm Hg, barring the effects of scarring and inflammation,” Crane said.
The study included 21 consecutive patients with refractory glaucoma who underwent Xen45 gel stent implantation from 2017 to 2019 in a single center. Refractory glaucoma was defined as previously failed surgical or laser procedures and/or uncontrolled IOP on maximally tolerated medical therapy.
Primary outcome was meeting success criteria, with complete success defined as 20% reduction in IOP without medications and qualified success defined as 20% reduction in IOP with medications.
“At 3 months, complete success was achieved by 25% of the patients and qualified success by 50%. At 6 months, the rate of complete success decreased to 17%, while qualified success increased to 67%. Mean IOP changed from preoperative 20.8 mm Hg to 14 mm Hg at 3 months and 16 mm Hg at 6 months. Mean number of medications changed from three preoperatively to 0.9 at 3 months and 1.5 and 6 months,” Crane said.
Four eyes experienced hypotony that resolved by month 3. IOP elevation occurred in four eyes, and one eye had exposed Xen implant and bleb leak. Four cases of hyphema resolved by month 3, and needle revision was performed in four cases. No significant change in visual acuity was reported.
“Further investigation with a larger sample size is necessary to understand long-term outcomes,” Crane said.
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Crane A, et al. XEN gel implant in refractory glaucoma: a retrospective study. Presented at: Association for Research in Vision and Ophthalmology annual meeting; June 12, 2020 (virtual meeting).
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