We have two eyes and for us to experience comfortable, efficient use of both eyes, they must first co-ordinate the eye aiming muscles. We need to know “where” to look before we can pay attention to the fine detail.
Converging when doing tasks up close, and releasing back when looking straight ahead for distance is an action that happens hundreds if not thousands of times a day. It must be done with extreme precision. Our perception of distance and space is critical for this. Small spectacle support lenses or prisms and vision therapy can be used to improve eye aiming ability if required.