Bupivacaine injection of eye muscles to treat strabismus

BACKGROUND: Bupivacaine injected into animal muscles induces a cycle of myotoxicity, degeneration, regeneration and hypertrophy of muscle fibres, without adverse effects on other tissues. This induced hypertrophy can be harnessed to treat strabismus. METHODS: Bupivacaine, 4.5 ml of a 0.75% solution, was injected into the right lateral rectus (RLR) muscle of a patient who had diplopia and who showed 14-prism-dioptres oesotropia. RESULTS: RLR paresis persisted for 7 days. Then, the RLR regained its abducting ability, and progressive improvement of alignment to 4-prism-dioptres oesophoria occurred over the next 33 days, with the elimination of diplopia. Alignment remained the same at 54 days after injection. Magnetic resonance imaging showed a focal increase in the size of the injected RLR of 58% in the posterior area, with reduced change in anterior portions of the RLR. CONCLUSION: Injection of bupivacaine to induce hypertrophy of the injected muscle and thus alter eye alignment was effective in our patient. This approach can be a useful addition to the treatment of strabismus.