Use of botulinum toxin A in the treatment of intermittent exotropia
Reviewed by Su Young

In this prospective cohort study, the authors aimed to evaluate the efficiency of botulinum toxin A (BTA) injection in the treatment of intermittent exotropia (IXT) and examine factors affecting treatment outcomes. Seventy-four patients diagnosed with any type of IXT were included in the study. BTA injection was performed by injecting five units of BTA (BOTOX®; Allergan) per muscle, 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 mean follow-up was 16.1 ±11.1 months (range 6 to 53 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. At the most recent examination, 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 (p < .001). Successful motor alignment (orthotropia within 10 PD for exodeviation) was achieved in 42 patients (56.7%). The success of treatment increased with a reduced amount of deviation at distance pre-BTA injection. It should be noted that study included both paediatric and adult patients, with a mean age of 11.2 ±9.8 years, ranging from 1 to 43 years. The same dose of BTA was also administered to all patients. The authors conclude that BTA injection into the lateral rectus muscles is an effective procedure for IXT. Benefits include less invasive and shorter time than surgery. The authors recommend that it as an alternative treatment option in small-medium angle IXT.

Use of botulinum toxin A in the treatment of intermittent exotropia: factors affecting treatment outcome.
Kunduracı MS, Kantarcı B, Erşan HBA, Tuğcu B.
SEMINARS IN OPHTHALMOLOGY
2022;37(5):626-30.