Background The treatment efficacy of botulinum toxin bilateral medial rectus injections for acute acquired concomitant esotropia (AACE) in adult is not clear. We characterize the effects of botulinum toxin injection in the treatment of AACE, especially in patients over 14 years old, and compared it with surgical treatment. Methods In this prospective, nonrandomized, controlled clinical study, patients with AACE in our hospital from March 2017 to March 2020 elected to receive bilateral medial rectus injections of botulinum toxin or to undergo extraocular muscle surgery. Ocular position and stereopsis were evaluated before and after treatment. Results A total of 60 patients were treated: 40 patients in the botulinum toxin group, and 20 patients in the surgery group. The botulinum toxin group included 31 cases ≥ 14 years of age and 9 cases < 14 years of age. After 1–3 botulinum injections, the cumulative initial success rate was 95% (38/40), and the recurrence rate was 22.5% (9/40). Nine children < 14 years of age were treated successfully, without recurrence. In the surgery group, the initial success rate after surgery was 75% (17/20), and the recurrence rate was 20% (4/20). There was no significant difference between groups in the rate of success rate or the rate of recurrence (P > 0.05). Conclusion The injection of botulinum toxin has a good effect on AACE in adults and children. The outcomes achieved with injected botulinum toxin are similar to those achieved with surgery. Trial registration ChiCTR, ChiCTR2000032544. Registered May 2, 2020, Retrospectively registered.

Background: The treatment efficacy of botulinum toxin bilateral medial rectus injections for acute acquired concomitant esotropia (AACE) in adult is not clear. We characterize the effects of botulinum toxin injection in the treatment of AACE, especially in patients over 14 years old,and compared it with surgical treatment.Methods: In this prospective, nonrandomized, controlled clinical study, patients with AACE in our hospital from March 2017 to March 2020 elected to receive bilateral medial rectus injections of botulinum toxin or to undergo extraocular muscle surgery. Ocular position and stereopsis were evaluated before and after treatment.Results: A total of 60 patients were treated: 40 patients in the botulinum toxin group, and 20 patients in the surgery group. The botulinum toxin group included 31 cases ≥14 years of age and 9 cases <14 years of age. After 1–3 botulinum injections, the cumulative initial success rate was 95% (38/40), and the recurrence rate was 22.5% (9/40). Nine children <14 years of age were treated successfully, without recurrence. In the surgery group, the initial success rate after surgery was 75% (17/20), and the recurrence rate was 20% (4/20). There was no significant difference between groups in the rate of success rate or the rate of recurrence (P>0.05).Conclusion: The injection of botulinum toxin has a good effect on AACE in adults with minimal squinting and in children. The outcomes achieved with injected botulinum toxin are similar to those achieved with surgery.Trial registration: ChiCTR, ChiCTR2000032544. Registered May 2, 2020，Retrospectively registered, http://www.chictr.org.cn/showproj.aspx?proj=52349