1. A method of optimizing an electrode tissue interface comprising: implanting at least one electrode in the vicinity of visual neural tissue; electrically stimulating the visual neural tissue through the at least one electrode, with a stimulation signal to the at least one electrode comprises pulses at a first frequency within a frequency range of greater than 100 Hz. and less than 10,000 Hz; measuring impedance of the electrode tissue interface to obtain an impedance measurement; electrically stimulating the visual neural tissue through the at least one electrode, with a stimulation signal to the at least one electrode comprises pulses at a second frequency within a range of greater than 100 Hz. and less than 10,000 Hz; and measuring impedance of the electrode tissue interface to obtain an impedance measurement.