Congenital factors: 1, abnormal development of the nucleus or/and nerves governing eye movements 2, abnormal development or absence of extraocular muscles and fascial tissues 3, abnormal development of the face and orbit 4, brain and eye damage caused by obstructed birth, intrauterine asphyxia, forceps assisted delivery, etc. 5, genetic factors Acquired factors: 1, children: adjustment factors (hyperopia), convergence or separation insufficiency, low vision in one eye (amblyopia or 2. Adults: neurological diseases, endocrine abnormalities, diseases of the five senses, traumatic brain injury, ocular trauma, orbital occupational diseases, viral infections, neuritis, myositis, abnormalities of extraocular fascial tissue, etc.