Double vision is a very common symptom in ophthalmology and can be caused by a variety of reasons, the common ones are as follows: First, ocular muscle weakness, because muscle weakness affects the movement of the extraocular muscles, so that both eyes do not rotate in a coordinated manner and the scene seen by both eyes is not exactly the same, thus in the brain’s vision cannot be fused into This causes double vision. Secondly, paralytic strabismus is caused by damage to the nerve or extraocular muscles, which makes the eye movement impaired, and the symptoms are especially obvious when the eyes are turned in a certain direction. Thirdly, restrictive strabismus is caused by orbital fracture or tumor in the orbit, which restricts the contraction of the extraocular muscles.