Spatiotemporal multiplexing on subretinal prosthesis increases selectivity of the network-mediated stimulation

Subretinal photovoltaic implants (PRIMA) provide form vision in patients blinded by age-related macular degeneration. The success of this approach is attributed in part to the network-mediated stimulation, which preserves many features of the natural retinal signal encoding. For efficient stimulation of bipolar cells (BC) with smaller pixels, electric field confinement should be relaxed, yet direct activation of the retinal ganglion cells (RGC) should be avoided. Here we present a new method for selective stimulation of bipolar cells using image multiplexing - sequential presentation of the image's components in several subframes. With sizes of the subframe islands optimized by computational modelling, the selectivity of network (BC) mediated retinal stimulation increased over 5 times in rats. Using this approach, electric field confinement can be relaxed, allowing pixels as small as 20 m to efficiently stimulate bipolar cells, while avoiding direct stimulation of RGCs and preserving high contrast of the pattern. This software-based improvement enables higher visual acuity of prosthetic vision without a change in implanted hardware.