Critical age of botulinum toxin treatment in essential infantile esotropia.

Objective: To assess the results of botulinum toxin treatment in 60 consecutive children with essential infantile esotropia.

Methods: Bilateral simultaneous injection of botulinum toxin into the medial rectus muscle was performed in 60 patients under direct visualization with an "open sky" technique. Fluothane/sevoflurane insufflation anesthesia was used. Each patient underwent a single bilateral botulinum toxin injection. Patient age at the time of injection ranged from 5-8 months.

Results: Mean patient age at the time of treatment for the 88% of patients who gained a good alignment (within +10 prism diopters [delta] of residual esotropia) was 6.5 months, while mean patient age at time of injection for the 12% of patients who were undercorrected or the deviation relapsed was 7.8 months. Follow-up averaged 5.2 years (range: 2-9 years, SD 2). No variation of the angle of strabismus was observed after 6 months from injection. In some patients with hyperopic refraction, plus lens corrections were prescribed during follow-up to stabilize the alignment.

Conclusions: Botulinum toxin can be effective in essential infantile esotropia when children are treated by age 7 months.