HOW THEY WORK In a true visual prosthetic, a video encoder (camera) transforms the visual world in front of a blind individual into electrical signals that are used to excite neurons at some point of the visual pathway. The video camera encoder will be a silicon retina that replaces some of the functions that the human retina performs, and then it makes what it sees into signal compatible with the neurons the encoder must stimulate. The signals from the encoder excite neurons either via a hard-wired percutaneous connection, or a telemetry link. "The stimulating electrodes must be implanted into visual pathway such that each electrode is able to excite only a small population of neurons in the vicinity of the electrode." (Normann, Richard. "Visual Neuroprosthetics Functional Vision for the Blind", in IEEE Engineering in Medicine and Biology, Jan-Feb. ’95, pg. 77) To improve the picture sent by the implants to the brain, electrodes the size of the neurons they intend to stimulate in the eye were developed. Kensall Wise at the University of Michigan created small high density electrode arrays out of silicon. In one model, the electrodes are .08 mm at their base, and taper to a sharpened tip. An array of hundreds of such electrodes can be implanted into cortical tissue about 1.5-2.0 mm below the cortical surface. This is not all of the design considerations involved, but it gives an idea of the direction that public research has gone in. A special pneumatic inserter that can shoot the arrays at high velocities to insert them into the cortical tissue was created by Patrick Rousche. This method provided limited cortical-based-map images. To further improve the picture, implants are being created that create a retinal map, rather than a cortical map. This can take advantage of the image forming properties of the human eye, and may give satisfactory images. At the current pace of public development, visual implants that restore sight are only a few years away from mass production. Meanwhile, the Network continues to create and use visual implants that are more sophisticated than what the public sector has been allowed to create. Bear in mind that these researchers use either foundation grant money or government grant money to operate. The Network is very careful about what technology is developed. Some excessively ambitious implant researchers (not visual, but other) have seen their work have a national security gag order thrown over them, and the research ends up muzzled from getting out to the public.