Incidence of Brainstem Anesthesia or Retrobulbar Hemorrhage after Retrobulbar Injection
Bibliographic record
Abstract
TOPIC: To determine the literature-pooled incidence of retrobulbar hemorrhage (RBH) and brainstem anesthesia (BA) after retrobulbar injection (RI). CLINICAL RELEVANCE: RBH and BA are both rare albeit potentially devastating complications of RI. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.021 | 0.061 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.013 | 0.026 |
| Bibliometrics | 0.009 | 0.008 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".