An artificial retinal device, implanted in the subretinal space of the eye in
persons with certain types of retinal blindness, induces artificial vision by electrical
stimulation of the remaining viable cells of the retina. The artificial retina
device includes a stimulating electrode unit preferably placed in the subretinal
space, and a tail-like extension housing a distant electrical return ground electrode
unit that may be placed in the vitreous cavity. The stimulating electrode unit
includes an array of electrode subunits. Each electrode subunit includes one or
more microphotodiodes electrically connected, for example, in series to provide
increased voltage and current to its microelectrode. The stimulating electrode
unit and the ground return electrode of the ground return electrode unit are preferably
disposed on opposite sides of the neuroretina to allow for efficient and high resolution
transretinal electrical stimulation of the neuroretinal cells. Additional photodiodes
may be incorporated into the circuitry of the artificial retina device to provide
additional bias voltage and current to the microelectrode subunits of the stimulating
electrode unit. In another preferred embodiment, the ground return electrode in
the tail-like extension is disposed in the capsular bag of the eye, after lens
nucleus and cortex removal, where it is electrically connected to an additional
bias photodiode or photodiodes.