Normal double vision in one eye is considered to be double vision, which may be caused by strabismus, brain tumor, stroke and other diseases. 1. Strabismus: the cause of this disease is more complicated, which may be related to eye trauma, viral infection, lack of extraocular muscles and other causes that lead to abnormal eye regulation function. Patients may suffer from diplopia, nausea, dizziness, photophobia, blurred vision and other symptoms. 2. Brain tumor: The common risk factor for the development of brain tumor is ionizing radiation, which may also be related to the differentiation of residual tissues in the embryonic development of the brain into tumors. Other risk factors include viral infections, allergic diseases and craniocerebral trauma. Because brain tumors can affect the central nervous system, leading to extraocular muscle dyskinesia, followed by diplopia, as well as vomiting, optic nerve papillary edema and other symptoms. 3. Stroke: the causes include intracranial and extracranial arterial stenosis, cerebral artery embolism, pathogenic microbial infection, and cerebral arterial malformation. Because embolus dislodgement will affect the central retinal artery obstruction, so the patient will have diplopia, vision loss and other ocular artery involvement. There are many causes of monocular and binocular double vision, patients need to go to the hospital, do a series of related examinations, to clarify the specific causes, and then treat the cause of the disease.