Fig. 2: Electric field with various implant geometries overlaid on retinal histology.

Electric field above the photovoltaic pixels (40 μm in width) of various geometries, with a potential relative to the middle of IPL (57 μm). a A bipolar pixel containing a central active and a circumferential return electrode. b A honeycomb-shaped pixel with elevated return electrode¹². c Two monopolar pixels without local returns, where the active electrode of the left pixel acts as an anode and the one on the right—as a cathode, collecting 75% of the anodal current. The remaining current is collected by a global return around the edge of the device. The bottom panels show the corresponding simulated electric fields overlaid on a histology image of a degenerate rat retina (current = 68 nA). Diagram of a bipolar cell with its axonal terminals in the middle of IPL in the left panel illustrates its position and size with respect to the field penetration depth. The arrows represent current magnitude on a log scale. Source data are provided as a source data file.