The Efficacy of Dose Increments of Botulinum Toxin A in the
Botulinum toxin is known to have a powerful chemodenervation effect, and it is a well-established alternative to incisional surgery for strabismus. This study aims to investigate the efficacy of dose increments of botulinum toxin A (BTA) for the treatment of specific ranges of angle deviation.

This was a prospective study that included patients presenting with esotropia who were managed by a single surgeon. Botulinum toxin was given in different dosages according to the size of deviation (11–19, 20–29, 30–39, and equal or more than 40 prism diopters (PD)), respectively. A successful outcome was defined as a deviation equal to or less than 10 PD in the last visit (a minimum of 6 months) following a single injection.

A total of 56 patients with esotropia were included. The mean pre-treatment angle of deviation was 38.6 ± 2.5 PD. Botulinum toxin A injection in a dose of 2.5 IU for the 11–19 PD angle of deviation showed the highest rate of successful outcomes (75%). According to the type of esotropia, partially accommodative esotropia showed the best response to the use of dose increments (59%). The incidence of ptosis post-botulinum toxin A injection was the least (37.5%) with the smallest dose (2.5 IU).

Botulinum toxin A usage in dose increments is safe, efficient, and might be more cost-effective with less incidence of BTA-associated complications. Different esotropia diagnoses have different clinical responses. However, larger studies are necessary to better predict the outcome of using dose increments.