Intermediate Outcomes of Styrene-Block-Isobutylene-Block-Styrene Microshunt, Gelatin Microstent, and Trabeculectomy: A Comparative Retrospective Cohort Study.

PURPOSE: To compare the 2-year surgical success rates, the complications, and risk factors for failure of the styrene-block-isobutylene-block-styrene (SIBS) microshunt, the gelatin microstent, and trabeculectomy.

DESIGN

Single-center, single-surgeon retrospective cohort study.

SUBJECTS: 142 eyes from 124 adult patients diagnosed with glaucoma (43 SIBS microshunt, 63 gelatin microstent, and 36 trabeculectomy).

METHODS

Consecutive eyes that underwent SIBS microshunt implantation, gelatin microstent implantation, and trabeculectomy were compared.

MAIN OUTCOME MEASURES: The primary outcome was the proportion of eyes achieving surgical success at 2 years, defined as (1) intraocular pressure (IOP) between 6 and 17 mmHg (inclusive) without the number of glaucoma medication classes (meds) (complete success) or with meds (qualified success); (2) no IOP readings >17 mmHg or <6 mmHg with clinical hypotony, on 2 consecutive visits; and (3) no surgical revision, reoperation, or loss of light perception. Secondary outcomes included success rates for IOP range of 6 to 14 and 6 to 21 mmHg, postoperative IOP, meds, complications, additional interventions, and risk factors for failure.

RESULTS

SIBS microshunt group included a significantly higher proportion of eyes with prior failed glaucoma filtering surgery (41.9% vs. 0% for gelatin microstent and 2.8% for trabeculectomy, respectively; P < 0.001). At 24 months, complete success rates in the 6 to 17 mmHg range were 72.1% for SIBS microshunt, compared with 50.0% for trabeculectomy (P = 0.034) and 38.1% for gelatin microstent (P < 0.0001). Qualified success was achieved in 83.7%, 66.7%, and 55.6%, respectively, with SIBS demonstrating superior outcomes to gelatin microstent (P = 0.003). In the multivariable analysis, the gelatin microstent (hazard ratio [HR]: 3.43; 95% confidence interval [CI]: 1.61-7.31) and combined cataract surgery (HR: 2.06; 95% CI: 1.27-3.35) were associated with increased hazard of failure, while age ≥70 years was associated with lower risk of failure (HR: 0.54; 95% CI: 0.30‑0.98). All procedures significantly reduced IOP and meds (P < 0.001). Complication rates were similar across groups, most resolving before 3 months. Needling was performed in 2.3% (SIBS microshunt), 30.2% (gelatin microstent), and 30.6% (trabeculectomy) of eyes, and 5-fluorouracil injections in 48.8%, 25.4%, and 50.0%, respectively. Revision rates were 4.7%, 7.9%, and 0%, respectively (P = 0.283), while reoperations were higher with gelatin microstent (15.9% vs. 2.3% and 2.8%; P = 0.022).

CONCLUSIONS

Despite higher-risk baseline profile, the SIBS microshunt achieved higher 2-year success rates than trabeculectomy and gelatin microstent across multiple IOP ranges, with comparable complications and fewer reoperations.

FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.