Diplopia in both eyes is caused by a disorder in the eye muscles or the brain nerves that control them. Possible causes include myasthenia gravis, diabetes, Graves’ disease, brain tumors, strokes, aneurysms, multiple sclerosis, throat cancer, and trauma (fracture of the orbital wall, causing the extraocular muscles to be trapped). Treatment methods mainly include (1) monocular occlusion or fogging method, which involves using only one eye to see and can alleviate the discomfort caused by diplopia. (2) For those with mild diplopia, a prism-corrective glasses can be used to correct the vision.