People with crossed eyes, a condition medically called strabismus, cannot see straight. Strabismus occurs when the eyes do not line up in the same direction, causing each of them to focus on a different object.
In normal eyes, a group of muscles work together to help a person's eyes focus on the same object. With crossed eyes, these muscles do not work together, causing each of the person's eyes to focus on a different object. Each eye sends a different image to the brain. The brain often becomes confused and learns to ignore one of the eyes. Strabismus can be corrected by using an eye patch, which is placed over the stronger eye to force the weaker eye to work harder, or through surgery on the eye muscles.