Visual evoked potentials after retrobulbar or periocular anaesthesia

The effect of the local anaesthetic agent, etidocaine, on the optic nerve function was examined at regional ophthalmic anaesthesia. Visual evoked potential (VEP) was recorded before and 15 minutes after injection of the anaesthetic agent in 19 patients scheduled for elective cataract surgery (seven retrobulbar and 12 periocular). Both the anaesthetised--that is, the eye to be operated on--and the fellow eye were examined. In the retrobulbar group, two patients displayed non-recordable VEPs while one had virtually non-detectable waves following the anaesthesia. In two retrobulbarly anaesthetised eyes, later peaks were unidentifiable while two other eyes had decreased amplitudes. In the periocular group, in nine patients, there was no clearcut effect on VEP resulting from the anaesthetic. In three patients of this group mild changes in the anaesthetised eyes were found. The differences in the effect of retrobulbarly or periocularly injected anaesthetics on VEP are probably due to the different concentration of the anaesthetic agent around the optic nerve.