To maintain focus, the target area for work should be within peripheral vision, ideally within the space created by cupping hands near the eyes.

“we never really want to be looking at a square or rectangle or target area for our work that is too far beyond our ears. How far is too far? Really, you want to try and keep the blinders on, or I should say the invisible blinders so that whatever you're looking at falls within the region of visual space in front of you, that is present if you were to cup your hands and put them right next to your eyes.”