Short Aqueous Stent to Subconjunctival Space

The XEN Gel Stent (Allergan) and PreserFlo Microshunt (formerly called InnFocus Microshunt; Santen Inc.) are 2 devices that shunt aqueous humor to the subconjunctival space. Unlike traditional plate-based tube implants, these devices do not have a plate attached to the subconjunctival portion of the tube.

In XEN Gel Stent implantation (Video 13-21), a clear corneal incision is created in the inferior cornea. The eye is filled with viscoelastic, and a goniolens is placed on the eye to visualize the superior angle. The injector is introduced into the eye, and the superior TM is pierced by the injector. The needle is driven through the sclera, exiting 3 mm posterior to the limbus into the subconjunctival space. The device is carefully injected into the subconjunctival space, and the needle is retracted. MMC is used to reduce postoperative fibrosis.

In the pivotal study for the FDA, 75% of patients had ≥20% reduction of IOP at 12 months, 32% required postoperative transconjunctival needle revision, and 25% had transient hypotony. Potential complications are similar to those of trabeculectomy and tube shunt, including choroidal effusion, tube erosion, prolonged hypotony, and infection. Of note, there was no comparator arm in this trial. In 2 retrospective studies, there was no significant difference in success rates between trabeculectomy and XEN Gel Stent surgery.

The PreserFlo Microshunt is an externally placed, nonplated tube implant currently undergoing FDA evaluation. A 4-year nonrandomized study showed that 80% of eyes attained an IOP <14 mm Hg from a baseline of 25 mm Hg.

• Grover DS, Flynn WJ, Bashford KP, et al. Performance and safety of a new ab interno gelatin stent in refractory glaucoma at 12 months. Am J Ophthalmol. 2017;183:25–36.

Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.