'Strabismus' is a term used to describe the abnormal positioning or direction of the eyeball. Normally, the eyeball is held in place and moves from side to side and top to bottom under the influence of small muscles which attach directly to the eyeball. Occasionally one muscle may be longer or stronger than the muscle located on the opposite side. This causes the eyeball to veer off in an abnormal direction. One or both eyes may be affected. If both eyes deviate towards the nose, the pet is referred to as cross-eyed. This is common in Siamese cats and is called 'medial' or 'convergent strabismus.' The eyeballs may deviate away from the nose, just the opposite of being cross-eyed, and this is called 'divergent strabismus.' This is common in Boston Terriers and is inherited in this breed.
Strabismus can also occur as a result of injury to some of the nerves going to the eye muscles. In addition, it may be seen if the dog has a disease of the vestibular system. The vestibular system is part of the ear and is what helps the dog (and us) keep our balance. If the vestibular system is not functioning normally, the dog may feel as though he is spinning, and his eyes will move abnormally to try to adjust to that.
If it is an inherited condition, no treatment is recommended as the abnormality is generally a cosmetic problem which does not affect the quality of life. If it is inherited, the breeding of affected individuals is not recommended.
For animals with injury to or disease of the nerves or the vestibular system, the underlying cause needs to be found and treated. Sometimes anti-inflammatory medications are helpful.