Oh dangit, now I have to perform work. Thanks for the papers. If I can understand that first one and follow some of the refs I might get a clue. Strange that this isn't on the tip of every researcher's tongue, no? 8 bits is such a convenient value that I may just use it with attribution to you...
I also had some difficulty getting a count of inputs and outputs, finally came up with 150-175M inputs -- counting all the rods and cones, significantly less (1-25M) when just counting the eyes as units -- and about 800 muscles for output.