Botox Instead of Strabismus Surgery (BISS)

Plain-language summary

The purpose of the study is to evaluate if strabismus can be successfully treated requiring less surgical interventions with a Botox-based treatment regimen compared to a purely surgery based treatment regimen. Experimental arm: Botulinum toxin injection in the horizontal extraocular muscles. Control (active comparator) arm: Strabismus surgery on the horizontal extraocular muscles. No investigational product is used. In Switzerland the standard procedure for treating large angle esotropia is surgery, which is performed on the horizontal eye muscles that may be either recessed or shortened leading to reduced or increased muscle function respectively. As an alternative to strabismus surgery, botulinum toxin (Botox) can be applied in extraocular muscles. Botox prevents the release of acetylcholine in the synaptic cleft and thereby blocks the neuromuscular transmission thus inducing a palsy. Current evidence on the use of Botox in strabismus is incoherent, is poorly supported by basic research findings and leaves dedicated clinicians in the dark. The objective is to shed light into this field of clinical research, which may help to guide future pediatric ophthalmologists in their management of strabismic patients. In a best case scenario, the results from this trial will prevent strabismus operation for many children with acquired large angle esotropia.

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