Excitability of bipolar and ganglion cells with retinal prosthesis: a modeling study

Bipolar cells are important targets for electrical stimulation with retinal prostheses in order to obtain focused visual perception. In a computer simulation study the excitability of three retinal cells are analyzed for small sized disk, spherical and rectangular electrodes at the surface of the retina. The main results are: i) disk electrodes have smaller threshold currents than spherical ones, ii) thresholds for ganglion cell axon has minimum at a dipole distance of 150 /spl mu/m iii) long rectangular electrodes parallel to the axons at the retinal surface seems to be good candidates for local selective stimulation.