Strabismus

Source: all about vision
Strabismus is a failure of the two eyes to maintain proper alignment and work together as a team.
If you have strabismus, one eye looks directly at the object you are viewing, while the other eye is misaligned inward (esotropia, "crossed eyes" or "cross-eyed"), outward (exotropia or "wall-eyed"), upward (hypertropia) or downward (hypotropia).
Strabismus can be constant or intermittent. The misalignment also might always affect the same eye (unilateral strabismus), or the two eyes may take turns being misaligned (alternating strabismus).


See more
http://www.allaboutvision.com/conditions/strabismus.htm