Do any of your characters suffer from tunnel vision? If so, what has caused it? What are they focussing so hard on they are missing other vital, important things? How does this affect their relationships with other characters? Do they even accept they have tunnel vision?
If your characters "come out" of having tunnel vision, when they look back at the period when they were under its influence, what is their reaction? Do they regret the time wasted in having so narrow a vision or just accept that was what they were then and move on?