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 fusion of the visual objects on the retinas of the 2 eyes.
Double vision may be secondary to thyroid eye disease, myasthenia graves, tumors of the orbit or brain, and cerebral aneurysms, to name a few. 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.