Optic nerve toxicity following retrobulbar application of 2% lidocaine and 0.75% bupivacaine in rabbits

Objective To investigate the optic nerve toxicity following retrobulbar application of 2% lidocaine and 0.75% bupivacaine in rabbits.Methods Ten normal rabbits were averagely and randomly divided into five groups as follows: normal control group,normal saline group,lidocaine group,bupivacaine group,lidocaine united with bupivacaine group,each consisting two rabbits(four eyes).No operation was applied to normal control group,but we injected retrobulbarly 1.0 ml normal saline,2% lidocaine and 0.75% bupivacaine into normal saline group,lidocaine group,bupivacaine group,respectively.To lidocaine united with bupivacaine group,we applied retrobulbarly 1.0 milliliter 2% lidocaine and 0.75% bupivacaine,respectively.Performances in eyes were observed at 24h and 48h,and all rabbits were sacrificed for electron microscopy of optic nerve at 48h postoperatively. Results No significant complications were observed.Both 2% lidocaine and 0.75% bupivacaine could demyelinate optic nerve,especially when administered together.Conclusions Not only 2% lidocaine or 0.75% bupivacaine presents toxic effects on optic nerve but they may have synergistic effects.