Photovoltaic retinal prosthesis with optically configurable confinement of electric field

A retinal prosthesis system, comprising:

• a near-the-eye display for a video stream projection onto a retinal implant,
• wherein the retinal implant comprises photovoltaic pixels which convert light from the display into an electric current flowing through a biological tissue to stimulate retinal neurons,
• wherein each pixel in the retinal implant comprises one or more photodiodes connected in series between an active electrode and a return electrode,
• wherein the active and return electrodes are coupled to an electrolyte of the biological tissue via a capacitive interface or a faradaic interface,
• wherein the return electrodes of the pixels are connected together, and
• wherein a sequence of images in the video stream projected by the near-the-eye display onto the retinal implant is designed to optically precondition designated pixels to become sufficiently conductive to serve as transient return electrodes by accumulating a bias voltage at an electrode-electrolyte interface in these pixels.

A retinal prosthesis, comprising:

• an array of photovoltaic pixels configured to provide retinal stimulus responsive to a received video stream,
• wherein the array of photovoltaic pixels has a common return electrode,
• wherein each pixel has an active electrode that is capacitively or faradaically coupled to a retinal tissue,
• wherein each pixel includes one or more photodiodes connected in series between the return electrode and the corresponding active electrode, and
• wherein each pixel further includes an optically controllable conductance element, wherein illumination of the array of photovoltaic pixels with a secondary illumination pattern selects one or more pixels of the retinal implant to act as local return electrodes by activating corresponding conductance elements.