Crossed eyes (strabismus) occurs when the eyes point in different directions. It can occur constantly or intermittently and affects approximately five percent of children. Male and female children are affected equally. Strabismus can occur as the result of problems with the eye muscles, the nerves of the eye or the brain. In adults, it is associated with certain conditions such as diabetes, high blood pressure, multiple sclerosis, myasthenia gravis or thyroid disorders.