The concept of a visual prosthesis for the blind or partially sighted is no
t a new one, indeed, for more than three decades this technology based trea
tment for blindness has appeared imminent. Despite the concerted efforts of
numerous physicians, scientists and engineers. the successful application
of a useful visual prosthesis remains elusive. The present review will ende
avour to describe past efforts, investigate the present state of the art an
d indicate the obstacles that must be overcome in order to bring an electro
nic visual prosthesis to fruition.