Diplopia (double vision) is often the first manifestation of many systemic disorders, especially muscular or neurologic processes.
An accurate, clear description of the symptoms (eg, constant or intermittent; variable or unchanging; at near or at far; with one eye [monocular] or with both eyes [binocular]; horizontal, vertical, or oblique) is critical to appropriate diagnosis and management. Binocular diplopia (or true diplopia) is a breakdown in the fusional capacity of the binocular system. The normal neuromuscular coordination cannot maintain correspondence of the visual objects on the retinas of the 2 eyes.
Double vision may be secondary to thyroid eye disease, myasthenia gravis, tumors of the orbit or brain, and cerebral aneurysms. Rarely, fusion cannot occur because of dissimilar image size, which can occur after changes in the optical function of the eye following refractive surgery (eg, LASIK) or after a cataract is replaced by an intraocular lens.