The first report of the experimental use of botulinum toxin relevant to ophthalmologists was published from Alan Scott’s laboratory in 1973, and concerned the creation of incomitant strabismus in rhesus monkeys by injection and paralysis of the medial rectus muscle.1 With the optimal dosage of botulinum toxin A, when the paralysis resolved a concomitant exodeviation persisted and it appeared that in these animals the agonist:antagonist muscle balance had been altered permanently. On this basis the technique appeared to be a possible alternative to strabismus surgery. The initial publications on the effect of botulinum toxin injection on concomitant strabismus in adults were open non-comparative studies, but appeared to substantiate the hypothesis that a permanent realignment of the eyes could be achieved.2 However, the strong tendency for recurrence of the deviation in the absence of sensory …