Strabismus (or amblyopia) is a condition caused by a malfunction of the muscles that control eye movement, preventing both eyes from aligning and focusing on one object together. With strabismus, the eyes can turn in (cross eyed), or turn up, out or down, causing symptoms like blurry vision, lazy eye (amblyopia), double vision, headache and more. The condition can be present at birth (congenital) or develop later, signaling the possibility of a serious neurological problem. There are many known causes, including Downs syndrome, cerebral palsy and stroke.