Treating strabismus by injecting the agonist muscle with bupivacaine and the antagonist with botulinum toxin.

PURPOSE: We report the results of injection of bupivacaine (BUP) and botulinum toxin (BT) into agonist and antagonist muscles, respectively, to treat horizontal strabismus.
METHODS: We treated both horizontal muscles of 7 patients with comitant horizontal strabismus, 2 patients with partial lateral rectus (LR) paralysis, and one elderly myopic patient with acquired esotropia, injecting the agonist muscle with BUP in concentrations of 0.75% to 3.0% and volumes of 3.0 to 5.0 mL, and the antagonist with BT in about half the usual therapeutic dose to prevent it from stretching the BUP-treated muscle during its regeneration following BUP myotoxicity. We reinjected BT in one patient who had an inadequate response from the initial BT dose.
RESULTS: The 7 comitant patients were corrected (on average) 19.7 prism diopters (Delta), from 28.3Delta to 8.6Delta, at 193 days after injection. Muscle volume increase after BUP injection was 5.8% at 158 days. One LR palsy patient without LR atrophy was changed 55Delta; the other, with LR atrophy, was corrected 4Delta. Two patients had transient vertical deviations from the BT injection. The myopic patient with esotropia was unchanged.
CONCLUSIONS: Injections of BUP and BT corrected 7 patients with comitant horizontal strabismus an average of 19.7Delta, about double the correction reported from BUP injection alone. BUP-injected muscles increased size by 5.8%. Of 2 patients with LR weakness, one without LR atrophy was changed by 55Delta, but another with LR atrophy was corrected only 4Delta.