When speaking to my players about vision, I focus on peripheral vision. I don't agree with yelling at players to "get their heads up." I think it's one of the most overused phrases in youth soccer coaches because at the top level, it's not true. Go and look at any goal scored and see when the last time the goal scorer looked at the goal or the goalkeeper. You'll find more often than not that the last time they looked up was 2 or 3 touches prior to the shot or up to 1 second before the shot. The primary example of this is Messi when he scores a goal or Ronaldo when he is dribbling. Focus on being able to see the ball, AND the surrounding players, not one or the other.