Use of Botulinum Toxin A in the Treatment of Intermittent Exotropia: Factors Affecting Treatment Outcome.

[PURPOSE] To evaluate the efficiency of botulinum toxin A (BTA) injection in the treatment of intermittent exotropia (IXT) and determine factors affecting treatment outcome.

[MATERIALS AND METHODS] A total of 74 patients diagnosed with any type of IXT were included in the study. BTA injection was administered into both lateral rectus muscles. Gender, refractive error, age, pre- and post-injection measurements of ocular deviation, age at the time of the first BTA injection, number of injections, duration of misalignment, age at the onset of misalignment, presence of amblyopia, presence of anisometropia, preterm birth history, type of delivery, presence of any neurological disorder, follow-up period, postoperative ptosis, and vertical deviation were recorded. The final angle of deviation was used in the statistical analysis. Successful motor alignment was defined as a deviation of ≤10 prism diopters (PD) at distance. The relationship of all factors with treatment success was analyzed using the binary logistic regression analysis.

[RESULTS] A total of 74 patients, 40 female and 34 male, were included in the study. All the patients were followed up for six to 53 months after the first BTA injection, and the mean follow-up was 16.1 ± 11.1 months. Before the first BTA injection of the patients, the mean amount of deviation was measured as 25.7 ± 14.2 (range, 0-60) PD at near and 37.1 ± 10.9 (range, 16-65) PD at distance. According to the most recent examination of the patients, the mean amount of deviation was 10.6 ± 9.8 (range, 0-45) PD at near and 16.4 ± 10.2 (range, 0-45) PD at distance. There was a statistically significant difference between the first and last examinations of the patients in relation to the amount of deviations measured at both near and distance (p < .001). Successful motor alignment (orthotropia within 10 PD for exodeviation) was achieved in 42 patients (56.7%). Thesuccess of treatment increased with the decreased amount of deviation at distance before the BTA injection.

[CONCLUSIONS] In patients with IXT, BTA injection into the lateral rectus muscles is an effective procedure, which is also less invasive and taking shorter time than surgery, and it can be considered as an alternative treatment option in those with small-medium angle IXT.