Esophoria is defined as an inward deviation of the eyes. Unlike esoTROPIA, which is a visible inward deviation of one or both eyes, esoPHORIA is only visible when testing eye position and breaking fusion. When fusion is broken (by moving a hand or cover paddle from one eye to the next), the eyes assume a position of rest, called the phoric posture. This position (phoria) may be inward (eso) or outward (exo). The result of an inward or outward phoric posture is that the eyes and brain must constantly coordinate to rotate and move the eyes to a straight-ahead position. If the coordination is lost, the eyes move out of alignment and a person sees double.