You know that dictionary game in which someone chooses an unusual word and everyone makes up a definition for it. Well, I've got a good word for you. Strabismus.

It's a condition in which a person's eyes don't point together on the same object at the same time. While one turns toward an object ahead, the other may look in or out or up or down.

Crossed eyes occur in just one type of strabismus. The defining factor in strabismus is that the eyes don't work together. It can cause eyestrain and headaches, as well as various vision difficulties such as with peripheral vision and depth perception.

What causes strabismus?

Some people are born with it. Sometimes it's a result of a problem with the part of the nervous system that controls the muscles of the eyes. In many cases, no cause is identifiable. If a person develops strabismus as an adult, it may be associated with a more serious condition such as stroke.

Treatments include physical therapy, vision therapy, and sometimes surgery to strengthen or weaken the eye muscles.