Botulinum toxin as a tool for testing the risk of postoperative diplopia

If preoperative examinations indicate postoperative diplopia, we generally would dissuade a patient from a squint operation. In this situation, a reliable test for diplopia can be done by injection of Botulinum toxin into an eye-muscle. Thus a predominantly transient paresis is produced during which there is parallelism for a sufficient period of time, so that the patient has time enough to experience disturbing double vision or its absence. In all 31 patients of this study a clear decision for or against an operation was possible, only in three cases was an operation contraindicated.