Electrical Stimulation With Wire Type Microelectrodes Placed Into the Optic Disc in Rabbit Eyes (Long–Term Study)

Abstract

Abstract: : Purpose: To determine the long–term efficacy of wire type microelectrodes implanted into the optic disc of rabbit eyes. Methods: Four platinum wire microelectrodes were implanted into the optic discs of 5 rabbit eyes for 4 to 6 months. Electroretinography (ERG) and visually evoked potentials (VEPs) were monitored. Electrically evoked potentials (EEPs) were elicited by bipolar electrical stimulation of the optic nerve. The morphological effects of the chronic implantation of the electrodes in the optic disc were evaluated by histological examination. Results: All electrodes remained stable in the implanted sites throughout the post–implantation period except for one electrode. No intraocular infection, inflammation, or vitreoretinal proliferation was observed in any eye. EEPs could be elicited from each pair of electrodes at all testing times. The mean threshold currents to evoke EEPs increased until 1 month after implantation, but remained stable thereafter until 6th month. The amplitude and implicit time of the a– and b–waves of the ERGs and P1 of the VEPs did not change significantly throughout the post–implantation period. Histological evaluation of the optic nerve head revealed slight tissue encapsulations surrounding the electrode tracks. Conclusions: Wire–type microelectrodes implanted into the optic nerve appears to be safe and effective up to 6 months. These findings indicate that the implantation of microelectrodes in the optic nerve may be useful for the future development of an optic nerve–based prosthesis.

Keywords: optic disc • neuro-ophthalmology: optic nerve • electrophysiology: non-clinical