Double vision (diplopia) occurs when a patient fixates on a single object, but perceives two objects instead. Caused by a number of disorders, diplopia can be monocular or binocular. Sudden onset diplopia is induced by abnormal relation of the visual axes. The symptoms are usually very disturbing and annoying to the patient.Monocular diplopia does not go away when either eye is closed. This type of diplopia can be caused by defects in the front part of the eye involving the cornea and lens, such as corneal scars, cataracts, or the need for glasses Binocular diplopia, however, does go away when either eye is closed. It is caused by a misalignment of the eyes, which can be secondary to many disorders, most often neurogenic (nerve related) or myopathic (muscle related). Cranial nerves III, IV, and VI, responsible for moving the eye, may produce double vision if any of their functions are disturbed. Myasthenia Gravis, which also affects eye muscles, may cause double vision. Slowly developing diplopia may suggest a growing tumor compressing the cranial nerves mentioned above. In elderly patients with intermittent diplopia, Giant Cell Arteritis and ischemic vascular disease must be considered as possible causes. Diplopia can also occur following eye surgery and injury to the orbit of the eye.