Background/AimsDetermine the efficacy of stand-alone implantation of the ab externo SIBS or poly(styrene-block-isobutylene-block-styrene) microshunt with mitomycin C in glaucomatous eyes, refractory to previous subconjunctival filtering surgery, over 1 year of follow-up.MethodsConsecutive retrospective cohort of patients with intraocular pressure (IOP) above target and previous subconjunctival filtering surgery, who received the microshunt between July 2015 and April 2019. Primary outcome was a complete success, with failure defined as IOP <6 mm Hg with vision loss, >17 mm Hg or <20% reduction in IOP without medications. Secondary outcomes included thresholds of 6 to 14 mm Hg and 6 to 21 mm Hg for both complete (no medications) and qualified (with medications) success as well as qualified success for thresholds of 6 to 17 mm Hg. Risk factors for failure, IOP, medications and complications were also assessed.Results85 eyes of 79 patients with a preoperative median IOP of 22.0 mm Hg (IQR 18.0–29.0) on four (IQR 3–4) medications were included. Postoperative median IOP was 13.0 mm Hg (IQR 10.0–17.0) on zero (IQR 0–2) medication at 1 year. 61.0% achieved complete success and 79.7% achieved qualified success. Mild-to-moderate disease was associated with failure (adjusted HR 2.37; 95% CI 1.23 to 4.59). Needling was performed in 11.8%, and 8.2% underwent anterior chamber reformation. Complications were transient, consisting of hyphaema, choroidal detachment and hypotony maculopathy, with 7.1% of patients undergoing reoperation.ConclusionsIn a group of high-risk eyes that had already failed at least one subconjunctival filtering surgery, the SIBS microshunt demonstrates reasonable surgical success over 1-year follow-up, with relatively few complications.
