A method for stimulating a subject's retina. The method comprising selecting at least a first and a second electrode each configured to apply current to a subject's retina, determining impedance for the at least first electrode and second electrode, and applying current to the subject's retina through the at least first and second electrode, wherein current to be applied by the first electrode and the second electrode is configured to be higher for the first electrode when the first electrode has an impedance lower than a second electrode's impedance.