Even the more sophisticated theory that the retinal image is transmitted as signals in the fibers of the optic nerve has the lurking implication of a little man in the brain. For these signals must be in code and therefore have to be decoded; signals are messages, and messages have to be interpreted. In both theories the eye sends, the nerve transmits, and a mind or spirit receives. Both theories carry the implication of a mind that is separate from a body. (Gobson, 1979, p. 61).But, the sophisticated theory does not have the lurking implication. That is the point of computational models of visual processing. They don't need homunculi to do image processing any more than computers need homunculi to do image processing.
In the background, regarding "messages" and "codes" Gibson is fixated on Shannon information which he took to be a matter of one individual (human being) communicating with another (human being). But, for better or worse, the talk of code, information, etc., has largely dropped this understanding of "code" and "information".
And, you don't need dualism either. The eye sends messages to other regions of the brain. What's wrong with that idea?