Trabeculectomy Bleb Characteristics in Relation to Bleb Success Using Anterior Segment Optical Coherence Tomography–A Systematic Review and Meta-Analysis

PRCIS: ASOCT features of greater bleb height, thicker bleb walls and lower reflectivity are associated with trabeculectomy success, supporting the ASOCT's utility in monitoring and predicting outcomes post-surgery through standardized imaging protocols. PURPOSE: To evaluate and quantify the relationship between bleb characteristics on ASOCT with surgical outcomes. METHODS: Literature search was conducted across Medline, Embase, Cochrane, and Scopus for studies from the past 20 years, until 16 September 2024 on "glaucoma", "trabeculectomy", and "ASOCT". Data collected included patient characteristics, each study's definition of bleb success, clinical outcomes, as well as bleb characteristics. A literature review was conducted on studies which could not be used for meta-analysis. RESULTS: 11 studies, with a pooled total of 528 eyes in 517 patients, were included in the final meta-analysis. Successful blebs had significantly higher mean bleb height (mean difference [MD] 0.38 mm, 95%-CI: 0.20-0.56 mm, P=0.002), greater maximum bleb wall thickness (MD 0.21 mm, 95%-CI: 0.07-0.35 mm, P=0.009), and decreased reflectivity (MD -48.9%, 95%-CI: -78.3 to -19.4%, P=0.010), compared to failed blebs. No significant differences were found in bleb fluid cavity height and bleb area. Narrative synthesis revealed that wider blebs, increased fluid-filled cavity height, increased number of microcysts, larger filtration opening widths, and multiform bleb walls were also associated with higher rates of bleb success. Early bleb parameters were statistically significant predictors of bleb success up to 12 months post-operatively. CONCLUSIONS: Greater bleb height, thicker bleb walls, and lower reflectivity on ASOCT are consistently associated with successful trabeculectomy outcomes. The ASOCT may be useful in predicting bleb success and in supplementing post-operative monitoring, hence guiding timely medical or procedural interventions, to ensure long-term bleb success.