Long-Term Effects of Botulinum Toxin A for Horizontal Concomitant Strabismus in Chinese Children

ABSTRACT

Introduction

For childhood strabismus, early surgical intervention improves both motor and sensory outcomes. Botulinum toxin type A (BTX-A) injection is an alternative to incisional surgery that is fast, less invasive, and preserves a more normal biomechanical construct. This study was undertaken to assess the safety and effectiveness of BTX-A for horizontal concomitant strabismus in children in our institution.

Patients and Methods

Records of all children less than age 18 years with follow-up at least 12 months who were treated with BTX-A for horizontal concomitant strabismus at Beijing Children’s Hospital between December 2014 and February 2021 were reviewed retrospectively. Bilateral injections of BTX-A (Henli, 1.25 IU to 5 IU/0.1 ml) were made into the medial or lateral rectus muscles according to the angle of deviation. Reinjection was permitted if the initial alignment was not satisfactory within 1 to 6 months post-injection. Motor success was defined as a final misalignment ≤10 PD. Sensory success was defined as the presence of any evidence of sensory fusion, distance stereopsis, or near stereopsis at the last visit.

Results

Seventy-one patients were included. Fifty-two had esotropia, and 19 had exotropia. There was a significant decrease in the angle of deviation in all treated patients. The overall motor success rate was 60.6%. The motor success rate was highest in children with esotropia <50 PD (81.5%). Motor success was better for children with partially accommodative esotropia and acquired non-accommodative esotropia (80%, 83.3%, respectively) than for children with infantile esotropia (47.4%). Compared with the esotropia group, the fusion was significantly higher in the exotropia group (p = .007), and the proportion of patients with stereoacuity of better than 100 sec arc was higher also in the exotropia group (71.4%, p = .007), evidence of sensory outcomes were significantly better in the exotropia group. Complications were few. Twenty patients (28.2%) developed transient ptosis after injections; transient vertical deviations were seen in 3 patients (4.2%); and subconjunctival hemorrhage was seen in 5 patients (7%).

Conclusions

BTX-A appears to be an effective treatment for the management of horizontal strabismus with motor outcomes best in children with acquired smaller-angle esodeviations. Children with exodeviations had better sensory outcomes in this cohort. A randomized controlled study comparing incisional surgery to BTX-A will be important for guiding future treatment decisions.

KEYWORDS:

• Botulinum toxin A
• childhood strabismus
• horizontal concomitant strabismus
• motor outcome
• sensory outcome

DATA AVAILABILITY STATEMENT

The data presented in this study are available in this article.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

AUTHOR CONTRIBUTIONS

J.J. wrote and L.L. revised the manuscript. All authors have read and agreed to the published version of the manuscript.

INSTITUTIONAL REVIEW BOARD STATEMENT

This study was approved by the Institutional Review Board of Beijing Children’s Hospital (IRB number: 2020-k-171) and followed the tenets of the Declaration of Helsinki.

INFORMED CONSENT STATEMENT

Informed consent was obtained from all patients involved in the study.

KEY CONTRIBUTION

BTX-A injection is an alternative to incisional surgery. This study proved that BTX-A appears safe for management of childhood strabismus and is an effective treatment with motor outcomes best in children with acquired smaller-angle esodeviations.

Additional information

Funding

This research was funded by the National Natural Science Foundation of China (No. 81970844) and R&D Program of Beijing Municipal Education Commission (No. KZ202110025039).