When in a fight or flight situation, your scope of vision actually decreases. This is called tunnel vision. Your peripheral vision decreases. This is something that we try to prevent by sparring. Sparring regularly teaches karate-ka to fight intensely without getting angry, afraid, or any other emotions that will distract you from effectiveness.
Many people, even karate-ka get angry after being hit, especially in the face. From there their form, focus, and thinking go straight out the window. Again, sparring regularly will decrease this.