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  • Ab externo microshunt shows promising 1-year outcomes

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    Review of: Intermediate Outcomes of a Novel Standalone Ab Externo SIBS Microshunt With Mitomycin C

    Schlenker M, Durr G, Michaelov E, et al. American Journal of Ophthalmology, July 2020

    Investigators examined 1-year outcomes of a novel standalone SIBS microshunt (Preserflo) with mitomycin C.

    Study design

    This retrospective, single-center interventional case series included 164 eyes with uncontrolled open-angle glaucoma without prior incisional glaucoma surgery who underwent placement of an ab externo SIBS microshunt (Preserflo, formerly known as the InnFocus Microshunt, Santen) with mitomycin C.

    Success was achieved if there were no consecutive IOP readings of 17 mm Hg or higher, no hypotony and at least a 20% reduction from decision IOP. Complete success was achieved without medication while qualified success if medications were utilized. Secondary outcomes included upper IOP thresholds of 14 mm Hg and 21 mm Hg with and without a 20% IOP reduction from baseline, median IOP, medications, risk factors for failure, interventions, complications, and reoperations.

    Outcomes

    Complete success was achieved in 76.9% of eyes, qualified success in 92.5%. Complete success was 75.6% with an IOP cut-off of 14 mm Hg and 76.9% for s cut-off of 21 mm Hg, while qualified success was achieved in 91.9% and 92.5%, respectively. In multivariate analysis, a mitomycin C dose of 0.2 mg/mL (vs. 0.4–0.5 mg/mL) and primary open-angle glaucoma (vs. secondary open-angle glaucoma) were the only risk factors for failure.

    Needling was performed in 8.5% of eyes. Two eyes received surgical revision, and 1 underwent reoperation.

    Limitations

    This study provides early/intermediate results of a novel device (Preserflo) from the experience at a single site in Canada. Prospective, comparative, long-term studies are necessary to compare this SIBS device to trabeculectomy (ongoing Phase 3 study) or the Xen45 gel stent. The concentration mitomycin C used here wasn't standardized and lower concentrations were a risk factor for failure.

    Clinical significance

    Having a device that can reliably reduce IOP and glaucoma drop burden while minimizing risk of hypotony and other vision-threatening complications is a welcome advance in glaucoma surgery. The bleb produced with Preserflo has very different characteristics than the traditional trabeculectomy bleb. The data from this study reports a relatively low rate of needling compared with currently available subconjunctival surgical options.