It was found that controllers found it much easier to operate the light pen if they could see more than just the tip. They also had to see part of the shaft to be able to use the pen efficiently. Feedforward is the idea of anticipating or planning. Everything you do or act out is already pre-planned by your brain. Feedforward does not cause any problems but feedback does.
Feedback is knowledge of results.
It can mean confirmation or disconfirmation. Children with apparent hand-eye coordination problems really have feedback problems instead and not feedforward problems. For example, when the child tries to draw a square or a circle, he comes up with a distorted version like this. The distortion in the square happens because the child tries to monitor his actions as he goes along. He stops at certain points, for microseconds.