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

We report the results of injection of bupivacaine (BUP) and botulinum toxin (BT) into agonist and antagonist muscles, respectively, to treat horizontal strabismus. 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. 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. 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.