Complications of Botulinum Toxin-A for Treatment of Esotropia in Children

Abstract

 

Purpose

 

To report operative complications in children treated for esotropia by botulinum toxin A (BTX-A) injection.

 

Methods

 

Subjects <17 years of age with esotropia were enrolled in a 9-month data-collection study following BTX-A injection of one or both medial rectus muscles. Subjects were managed as per investigators’ routine clinical practice. Demographic, historical, and pre-injection clinical data as well as details of the BTX-A injection and perioperative complications were collected at enrollment. Post-injection data from each visit through 9 months was collected retrospectively.

 

Results

 

Twenty-seven subjects were enrolled at 13 sites. Esotropia onset occurred before 6 months of age in 13 (48%) subjects and after 6 months of age in 14 (52%). Eight (30%) subjects had prior strabismus surgery, and 1 (4%) had prior BTX-A injection. Mean age at injection was 3.9 ± 3.3 years (9 months to 13.8 years). BTX-A injection was unilateral (n=7) or bilateral (n=20) and dosage ranged from 3.0 to 6.0 units per muscle. Preoperative esodeviation, measured by prism and alternate cover test, ranged from 10 to 65 PD (mean = 26 PD) at distance and from 12 to 65 PD (mean = 28) at near. Four of 27 subjects (15%; 95% confidence interval [CI] = 4% to 34%) experienced a complication from the injection. One subject (4%; 95% CI = 0% to 19%) had a left eye scleral perforation which was noted at the time of injection and was treated by laser retinopexy the same day with good visual and motor outcomes. Three subjects (11%; 95% CI = 2% to 29%) developed tonic pupil noted at the first post-injection visit. All three cases occurred in the left eye of subjects who underwent BTX-A injection by the same surgeon, and were characterized by delayed denervation hypersensitivity to pilocarpine 0.125%. The anisocoria diminished during the data collection period, and there were no visual deficits.

 

Conclusions

 

Complications of BTX-A injection were encountered in this small cohort of children with esotropia. Globe perforation is a well-known complication of periocular injection. However, there are few reports of tonic pupil after BTX-A injection. The mechanism of action is unknown, but it may be direct trauma to the ciliary ganglion. Other possible explanations include anticholinergic toxicity from intraconal diffusion of BTX-A affecting the ciliary ganglion and/or intraocular diffusion affecting the pupillary sphincter.