  Two computational models to be used as tools for experimental research on the
retinal implant are presented. In the first model, the electric field produced
by a multi-electrode array in a uniform retina is calculated. In the second
model, the depolarization of the cell membrane of a probe cylinder is
calculated. It is shown how these models can be used to answer questions as to
cross talk of activated electrodes, bunching of field lines in monopole and
dipole activation, sequential stimulation, etc. The depolarization as a
function of time indicates that shorter signals stimulate better, as long as
the current does not change sign during stimulation.
