Efficacy of botulinum toxin in the treatment of intermittent exotropia

Multiple surgical interventions are burden to patients with intermittent exotropia (IXT) due to a high recurrence rate. This study was designed to evaluate the efficacy of botulinum toxin injection in the treatment of intermittent exotropia (IXT).

A total of 21 patients with IXT, who had a far deviation of less than 40 prism diopters (PD), were enrolled. All cases were followed for at least 6 months with non-surgical management and had decremented fusional control (increasing 3 or more scores in Newcastle Control Score [NCS]). Botulinum toxin was injected (10 units Dysport) to both lateral rectus muscles. Fusional control, sensory and motor status were evaluated at 1 day, 1 week, and 1, 3, and 6 months after injection to compare with the pre-injection values.

Fusional control (based on NCS) showed a significant improvement during 6-month follow-up. Mean NCS was 4.4±0.8 SD before botulinum toxin injection and 1.4±0.4 SD after 6 months (p<0.001). Evaluation of sensorial status with Worth Four Dot Test (WFDT) also demonstrated an improvement of fusion (the percentage of patients demonstrating fusion on WFDT were 10.5% before injection and 61.5% after 6 months). The mean far and near deviations decreased during 6 months of follow-up examination. Satisfactory outcome (stable binocular alignment of the eyes to an orthophoria+/-10 PD in primary position) for far distance was achieved in 38.1% at 6 months. The percentage of satisfactory outcome at near was 86% at 6 months follow-up examination.

Botulinum toxin injection to lateral rectus muscles seems to be a promising procedure in the management of fusional control, far and near deviations in patients with intermittent exotropia in short time.