Botulinum toxin injections for strabismus may be given without electromyography

Neuro-Ophthalmology/Orbit, Pediatric Ophth/Strabismus

This study compared open- and closed-sky injection techniques without electromyographic assistance for botulinum toxin injections for horizontal strabismus.

Study design

This multicenter retrospective chart review included 135 patients aged 1–50 years from Egypt and Saudi Arabia; 68% had esotropia and 32% had intermittent exotropia. One hundred four patients received closed-sky injections of botulinum toxin and 31 received open-sky injections; doses ranged from 2.5 to 15 IU. Closed-sky injections were given directly through the conjunctiva and open-sky injections were delivered under direct visualization of the rectus muscle after isolation though a fornix incision.


Success, defined as <10 PD of deviation after 6 months follow-up, was achieved in 59% of patients in the closed-sky group and 44% of patients in the open-sky group. Transient ptosis and vertical deviations were observed in 56% and 33% of all patients, respectively. No serious complications were reported. The average botulinum toxin doses were 4.47 IU in the closed-sky group and 7.64 IU in the open-sky group.


Factors that influenced the decision to pursue the open- or closed-sky technique were not discussed or recorded. Additionally, the dose of botulinum toxin was significantly different between the two techniques. For these reasons, and the general limitations of retrospective studies, the ability to compare the injection techniques is limited. The age range in both groups was wide, and this could limit the overall significance of the findings, as prior research has demonstrated less success with these injection techniques in older children.

Clinical significance

The perceived need for electromyographic assistance could limit the adoption of botulinum toxin to treat strabismus. This study showed similar rates of success for no electromyography and electromyographic assistance. No clear benefit to injection under direct visualization (open sky) was identified, though more research is needed.

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