Electrical field analysis of extracellular electrical stimulation of optic nerve with spiral cuff electrode

Extracellular electrical stimulation of optic nerve can evoke both excitatory and localized visual sensations. These nerve responses are a potential substrate for restoring some function of vision to blind or near-blind patients. Optic nerve stimulation is a developing therapeutical method to treat blind subjects who still have functional retinal ganglion cells. However, the small diameter of optic nerve presents a challenge to determine the optimal geometry and position of spiral cuff electrode for evoking these responses. In order to determine the optimal spiral cuff electrode structure, a finite element model of optic nerve and surrounding structures were generated to simulate extracellular electrical stimulation. During simulation, variety of electrode structures were applied, and thickness of cerebrospinal fluid (CSF) was considered. Numerical calculations were performed by means of finite element method in three dimensions. The stimulation results indicate that bipolar electrodes can excite nerve, but the stimulation of tripolar electrodes structure is more effective. The thickness of CSF influences the stimulation results.