Rat extraocular muscle regeneration. Repair of local anesthetic-induced damage

Local anesthetics that are commonly used in ophthalmic surgery (0.75% bupivacaine hydrochloride, 2.0% mepivacaine hydrochloride, and 2.0% lidocaine hydrochloride plus 1:100,000 epinephrine) were injected into the retrobulbar area of rat eyes. Controls were injected with physiological saline. All three anesthetics produced massive degeneration of the extraocular muscles. Muscle degeneration is followed by regeneration of the damaged muscle fibers. In addition to muscle damage, severe damage was also seen in harderian glands, especially after exposure to mepivacaine and lidocaine plus epinephrine. With these findings in rats, it is hypothesized that the temporary diplopia sometimes seen in patients after ophthalmic surgery might be due to anesthetic-induced damage to the extraocular muscles.