One of the applications of arrays of microelectrodes is the retinal implant. Here is an example of an acute test of electrical stimulation of a rabbit’s eye, using a microelectrode array positioned on the retinal surface (ganglion cell layer). We stimulated it with different currents, in order to evaluate the “brain’s response” (electrically evoked potentials, in terms of amplitude and latency).
Publication: http://iopscience.iop.org/1741-2552/12/1/016006