The retinal prosthesis test device is comprised of a thin wafer of glass made
from nanochannel glass (NGC) with very small channels perpendicular to the plane
of the wafer filled with an electrical conductor forming microwires. One surface
of the glass is ground to a spherical shape consistent with the radius of curvature
of the inside of the retina. The NGC is hybridized to a silicon de-multiplexer
and a video image is serially input to a narrow, flexible micro-cable and read
into a 2-D array of unit cells in a pixel-by-pixel manner which samples the analog
video input and stores the value as a charge on a MOS capacitor. After all unit
cells have been loaded with the pixel values for the current frame, a biphasic
pulse is sent to each unit cell which modulates the pulse in proportion to the
pixel value stored therein. Because the biphasic pulses flow in parallel to each
unit cell from a global external connection, the adjacent retinal neurons are all
stimulated simultaneously, analogous to image photons stimulating photoreceptors
in a normal retina. A permanent retinal implant device uses a NGC array hybridized
to a silicon chip, the image is simultaneously generated within each cell through
a photon-to-electron conversion using a silicon photodiode. The photons propagate
directly through into the backside of the device. Electrical power and any control
signals are transmitted through an inductively driven coil or antenna on the chip.
The device collects the charge in storage capacitors via the photon-to-electron
conversion process, stimulates the neural tissue with biphasic pulses in proportion
to the stored charges, and resets the storage capacitors to repeat the process.