Botulinum Toxin Type A Injection Effective for Some Types of Strabismus, AAO Says

Marilynn Larkin

August 02, 2021

NEW YORK (Reuters Health) — Extraocular muscle injection of botulinum toxin type A (BTXA) achieves outcomes similar to eye muscle surgery for nonparalytic, nonrestrictive horizontal strabismus, according to a newly released report from The American Academy of Ophthalmology (AAO).

"BTXA is a good alternative to eye muscle surgery for certain clinical situations," Dr. Gil Binenbaum, clinical spokesperson for the AAO and chief of the division of ophthalmology at Children's Hospital of Philadelphia told Reuters Health by email. "Both modalities can successfully treat strabismus, and each approach has advantages and disadvantages that might make it preferable in a given situation."

Referring to the report, published in Ophthalmology, he said, "While the amount of level I evidence is low, there is still fairly consistent evidence across many studies demonstrating the effectiveness of BTXA for strabismus. And there is randomized clinical trial evidence that BTXA is effective as an alternative treatment for reoperations following prior eye muscle surgery."

"Our systematic review found that as a whole, the literature clearly suggests that BTXA and eye muscle surgery have comparable motor success rates for basic strabismus," he continued. "However, there is limited evidence about sensory outcomes, and reason to think that the delayed time it takes a couple of sets of BTXA injections to achieve good alignment could negatively affect sensory outcomes compared to eye muscle surgery, which achieves that alignment more quickly."

"Ophthalmologists who treat strabismus may consider adding BTXA to their armamentarium," he said. "It is easy and quick to perform, it can work as well as eye muscle surgery, and for some children it may be preferable. It may be worth discussing the relative advantages and disadvantages with parents."

Dr. Binenbaum and colleagues searched the literature up to 2021 and identified 14 articles that met the inclusion criteria: randomized or nonrandomized comparative studies, or case series with a minimum 50 patients evaluating extraocular muscle BTXA injection for initial or repeat treatment of horizontal, nonparalytic, nonrestrictive strabismus, with at least six months of follow-up.

The studies included two randomized clinical trials, three nonrandomized comparative studies, and nine case series. The five comparative studies were graded level-II evidence, and the nine case series were graded level III.

Successful motor outcomes after BTXA injection were relatively consistent across four of the five comparative studies at 60%, after adjustment for differential selection bias in one study. Outcomes after surgery were not significantly different from those with BTXA, ranging from 66% to 77%, with a mean follow-up of 23 to 75 months.

In the fifth level-II study, success was significantly higher with BTXA injection than with surgery (94% vs. 72%).

The level-III BTXA case series demonstrated higher motor success rates of 87% to 89% when children were treated in two muscles at a time; rates were lower in adults treated with a single-muscle BTXA injection.

Dr. Sean Donahue, Sam and Darthea Coleman Chair in Ophthalmology at Vanderbilt University School of Medicine in Nashville and Chief of Pediatric Ophthalmology, Monroe Carell Jr Children's Hospital at Vanderbilt, commented on the paper in an email to Reuters Health.

"This is a very important summary report written by several well-respected pediatric ophthalmologists," he said. "Botox was originally developed for the treatment of children and adults with strabismus, but has not achieved the popularity of standard surgery."

"Most pediatric ophthalmologists are reluctant to use Botox as the primary treatment for children with eye misalignment," he said. "I believe this is mostly because their anecdotal experiences do not support the notion that the success rates are similar."

"Papers like this one require us to pause and think about whether or not treatment with Botox should again be considered for a select set of these patients," Dr. Donahue concluded.

SOURCE: https://bit.ly/3j3FoFz Ophthalmology, online June 25, 2021.

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