Botulinum toxin type A has been used to treat numerous types of strabismus in children and adults as both an adjunctive and alternative therapy. A recent report from the American Academy of Ophthalmology found extraocular muscle Botox injection achieved a high success rate of motor alignment comparable with eye muscle surgery for small to moderate angle, nonparalytic, nonrestrictive horizontal strabismus.
Still, the authors cautioned that good alignment may require multiple injections, and the jury is still out on whether sensory outcomes would be the same between Botox and eye muscle surgery in young children.
The findings were based on a literature review of 14 studies consisting of two randomized clinical trials, three nonrandomized comparative studies and nine case series with a minimum of 50 patients who had extraocular muscle Botox injection for initial or repeat treatment of horizontal, nonparalytic, nonrestrictive strabismus with at least six months of follow-up. The comparative studies were graded level II evidence, while the case series were graded as level III evidence.
Successful motor outcomes after Botox injection were relatively consistent across four of the five comparative studies at 60% when adjustment was made for differential selection bias in one of the studies. In these four studies, successful motor outcomes after surgery ranged from 66% to 77% with a follow-up between 23 to 75 months, and the results weren’t significantly different from Botox injection. In the fifth level II study, success was notably higher with Botox injection compared with surgery: 94% vs. 72%, respectively.
Additionally, the level III Botox case series demonstrated higher motor success rates between 87% to 89% when children were treated in two muscles at a time. On the other hand, the rates were lower in adults treated with single-muscle Botox injection.
Both esotropic and exotropic patients were represented in the case series. Although second or third sets of Botox injections were not required in many cases, the cumulative successful motor alignment rate increased when these additional sets of injections were added to the treatment protocol.
One noncomparative case series suggested that very early use of Botox, perhaps even before most surgeons would consider eye muscle surgery, may result in good motor alignment without the need for surgery; however, this hypothesis requires further evaluation, the researchers said.
Despite the findings, a well-designed, randomized control trial is warranted to confirm or refute the equivalency of Botox injection to eye muscle surgery for motor alignment, the authors suggested. Additionally, a prospective study of sensory outcomes is needed, since it’s not clear if faster ocular realignment from eye muscle surgery has a benefit compared with Botox, particularly if two or three sets of injections are required over a six- to nine-month period to obtain good alignment, they added.
Binenbaum G, Chang MY, Heidary G, et al. Botulinum toxin injection for the treatment of strabismus, a report by the American Academy of Ophthalmology. Ophthalmology. June 25, 2021. [Epub ahead of print].