This case-control study (n=117 AACE patients, Beijing Tongren Hospital, July 2021–January 2025) examined baseline and early postoperative predictors of needing a second botulinum toxin type A (BTA) injection within 6 months of initial bilateral medial rectus injection for acute acquired concomitant esotropia (AACE).
48% of patients (56/117) required reinjection within 6 months. Baseline anisometropia (≥1.0 D) independently raised reinjection odds 2.8-fold (OR=2.789, 95% CI: 1.183–6.576). Residual distance deviation at 3 months added further predictive value (OR=1.315 per prism diopter, 95% CI: 1.069–1.619). A combined model achieved AUC=0.810; a cutoff of >5.23 PD at 3 months had 82.0% specificity for reinjection. Patients with both risk factors had an 81.8% reinjection rate vs. 18.2% with neither.
- Single tertiary referral center limits generalizability; no external validation cohort. - Reinjection was based on actual receipt (not protocol-defined criteria), so patients who declined reinjection were classified as non-reinjection, likely biasing effect estimates toward the null. - Long-term follow-up beyond 6 months was available for only 33% of non-reinjection patients.
Check for anisometropia (≥1.0 D) before BTA injection in AACE — it nearly triples the odds of needing a second shot within 6 months. At the 3-month visit, a residual distance deviation >5 PD (with full correction) should trigger closer monitoring and early discussion of reinjection or surgery.
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