  Three critical improvements for present day and future retinal vision
implants are proposed and discussed: (1) A time profile for the stimulation
current that leads predominantly to transverse stimulation of nerve cells; (2)
auxiliary electric currents for electric field shaping with a time profile
chosen such that these currents have small probability to cause stimulation;
and (3) a local area scanning procedure that results in high pixel density for
image/percept formation (except for losses at the boundary of an electrode
array).

Neurons and Cognition