Incidence of Brainstem Anesthesia or Retrobulbar Hemorrhage after Retrobulbar Injection: A Systematic Review and...

To determine the literature-pooled incidence of retrobulbar hemorrhage (RBH) and brainstem anesthesia (BA) after retrobulbar injection (RI).

RBH and BA are both rare albeit potentially devastating complications of RI.

Prospectively registered meta-analysis (CRD420251041837). Central, Embase, and Medline were searched from inception to April 16th, 2025, for studies which reported the incidence of RBH or BA after RI. Complication incidence with patient and study characteristics was collected. Risk of bias and certainty of the body of evidence were assessed using Cochrane risk of bias-2 or risk of bias in nonrandomized studies - intervention (ROBINS-I) and the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) tool, respectively. Pooled incidence estimates were generated using random-effects meta-analyses of proportions via generalized linear mixed models with logit transformation. Preplanned subgroup analyses were performed, stratified by year (before versus after 2005), concomitant orbital compression maneuver, needle gauge, and number of injections.

We included 22 articles (n = 196 113 injections). The pooled incidence of RBH and BA were 0.10% (95% confidence interval [CI]: 0.03%-0.42%) and 0.23% (95% CI: 0.16%-0.34%), respectively. Although direct comparison was not statistically feasible, there was a significant between-subgroup difference of RBH incidence between patients undergoing 0.12% (95% CI: 0.01%-1.01%) or forgoing orbital compression 2.29% (95% CI: 0.74%-6.86%). Further, there was a significant between-subgroup difference of RBH incidence between the singular (0.47% [95% CI: 0.18%-1.24%]), multiple (0.04 [95% CI: 0.04%-0.04%]), or supplemental injection (0.35% [95% CI: 0.02%-7.09%]) subgroups. There was no significant subgroup-level difference in RBH incidence for studies published before versus after 2005. Finally, no significant subgroup-level difference was noted for RBH incidence across 23G (0.17% [95% CI: 0.01%-4.77%]), 25G (0.17% [95% CI: 0.02%-1.21%]), and 27G (0.04% [95% CI: 0.00%-2.67%]) needle gauge subgroups. Subgroup analyses for BA were precluded by insufficient data.

Low-certainty evidence (GRADE) supports that the pooled point estimates of RBH and BA were 0.10% and 0.23%, respectively. The certainty of evidence was downgraded for imprecision and indirectness, reflecting rare events and predominance of observational data. While subgroup analyses suggested significant differences of RBH incidence across strata of orbital compression maneuvers and number of injections, there was insufficient data to perform a comparative meta-analysis. Dedicated comparative studies of these potential factors should be pursued.

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