Crossed eyes are a commonly used term for the technical phrases esotropia.
This condition occurs where either eye may look straight ahead and the other eye will be turned inward toward the nose. The condition develops generally in early infancy or childhood. Many children during the first three to four months of life will have some intermittent crossing of their eyes. However, persistent crossed eyes in young children after the age of three to four months should be considered a serious condition. The eye that is turned begins to be ignored by the brain and eventually that image can be fully suppressed.