  The design and benchtop operation of a wireless miniature epiretinal
stimulator implant is reported. The implant is optically powered and controlled
using safe illumination at near-infrared wavelengths. An application-specific
integrated circuit (ASIC) hosting a digital control unit is used to control the
implant's electrodes. The ASIC is powered using an advanced photovoltaic (PV)
cell and programmed using a single photodiode. Diamond packaging technology is
utilized to achieve high-density integration of the implant optoelectronic
circuitry, as well as individual connections between a stimulator chip and 256
electrodes, within a 4.6 mm x 3.7 mm x 0.9 mm implant package. An ultrahigh
efficiency PV cell with a monochromatic power conversion efficiency of 55% is
used to power the implant. On-board photodetection circuity with a bandwidth of
3.7 MHz is used for forward data telemetry of stimulation parameters. In
comparison to implants which utilize inductively coupled coils, laser power
delivery enables a high degree of miniaturization and lower surgical
complexity. The device presented combines the benefits of implant
miniaturization and a flexible stimulation strategy provided by a dedicated
stimulator chip. This development provides a route to fully wireless
miniaturized minimally invasive implants with sophisticated functionalities.
