Objective: To study the outcomes and factors of muscle surgery for exotropia at Songklanagarind Hospital.

Design: A retrospective descriptive study.

Materials and methods: A review was made of medical records for patients who had muscle surgery for exotropia between January 1999 and December 2003. The angle of deviation and binocularity status before and after surgery were examined, follow up for at least 6 months.

Results: Forty five patients were classified into two groups. Group1 included; 25 patients (55.6%) had intermittent exotropia and group 2; 20 patients (44.4%) had constant exotropia. The average follow up time was 25±20.39 months (range 6-79 months). After surgery 96% of patients with intermittent exotropia had alignment within 10 Prism diopters, compared to 80% of patients with constant exotropia. The binocularity was improved in 60.9% of patients with intermittent exotropia and 31.2% of those with constant exotropia. The binocularity was improved mostly to patients with age of 3.1-9 years at the time of surgery.

Conclusion: The success rate was higher in intermittent exotropia group. The patients with exotropia who had age of 3.1-9 years at the time of surgery could did gain binocularity.