Botulinum toxin injection without electromyographic guidance in consecutive esotropia

Purpose To investigate the efficacy of botulinum toxin injection without electromyographic guidance for the treatment of consecutive esotropia. Methods A retrospective study was performed on 49 subjects with consecutive esotropia who received botulinum toxin injection in the medial rectus muscles without the use of electromyographic guidance. Treatment was considered successful if the final ocular alignment was orthotropic or esodeviation was <= 10 prism diopters (PD) during distant fixation. Results The mean age was 15.2 +/- 8.3 years. The mean esodeviation before injection was 21.8 +/- 9.1 PD at distance and 21.3 +/- 8.3 PD at near. The mean number of injections per patient was 1.3 +/- 0.7, and 46 patients (93.9%) received two or fewer injections. At 6 months after the final injection, the mean angle of esodeviation was 7.3 +/- 6.0 PD at distance and 7.5 +/- 6.6 PD at near (all p<0.001), and 69.4% showed successful alignment. By multivariate analysis, an initial postoperative esodeviation of <= 18 PD at one month after exotropia surgery was considered to be a predictive factor for successful botulinum toxin injection (P = 0.007). Vertical deviation and/or ptosis occurred in 4 patients (8.2%) at two weeks after injection, which all resolved within three months. There was no recurrence of exotropia up to the final follow-up examination. Conclusion Botulinum toxin injection without electromyographic guidance is safe and effective in the treatment of consecutive esotropia without causing recurrent exotropia. Successful botulinum toxin injection is likely in patients with an initial postoperative esodeviation of 18PD or less at one month after exotropia surgery.