An apparatus facilitating the delivery of electrical stimulation to physiologically excitable
retinal nerve cells includes: (a), a
receiver / decoder / stimulator comprising a
semiconductor integrated circuit and other components hermetically sealed within a
capsule, implanted and fixed within the eye of the patient such that it may receive power, and decode information from (b), an externally worn
image processor /
encoder /
transmitter comprising an
image detector, an
image processor capable of translating the image into an array of discreet pixels of varying intensity, encoding the pixel information into a series of discreet data bursts representing the chosen
current amplitude,
pulse duration, stimulating
electrode or electrodes, and
reference electrode or electrodes, and transmitting this data to the
receiver / decoder / stimulator through a tuned, inductive
communication link such that the
system may deliver controlled, charge balanced, diphasic,
constant current stimulus pulses to (c), discreet metallic electrodes on a flexible,
multiple site electrode array implanted on, near or under the surface of the
retina. The apparatus provides for flexibility in the
external image processing system such that future advancements in
processing techniques shall not require revision
surgery or modification to the implanted
receiver / decoder / stimulator. Safeguards to protect the patient from the delivery of inappropriate stimulus are incorporated into the apparatus, and a method of external collection of
diagnostic data from the implanted receiver / decoder / stimulator is described.