Double vision, also called diplopia, can be a symptom of serious illness, such as a tumor, blood clot or trauma--or simply a sign of visual fatigue or an incorrect eye glass prescription. Children with disabilities such as Down syndrome or cerebral palsy may experience diplopia due to eye-muscle dysfunction or misalignment. Other causes include neurological diseases and inflammation. Diplopia can be binocular, when using both eyes, or monocular, when using only one eye.
According to Eyerobics.com, diplopia is usually a symptom of the condition called strabismus. The eyes are misaligned and may turn inward, outward, upward or downward. Strabismus does not always causes double vision, but when it does, a child may tilt or turn his head to suppress one eye--avoiding the double image. Optometrist Dr. Mitchell Scheiman, author of "Understanding and Managing Vision Deficits" stresses the importance of early detection and treatment of this disorder because suppression of an eye can cause deterioration or lack of development of visual acuity. Monocular double vision is much more rare than the binocular type. Johns Hopkins professor of ophthalmology Susan B. Bressler reports that monocular double vision can be caused by astigmatism, dry eye, some types of retinal problems or cataracts. Astigmatism is a common and often treatable condition where the cornea is irregularly shaped. Other serious conditions that may cause double vision include displacement of the lens and retinal detachment.
Diseases that may cause double vision include thyroid conditions, multiple sclerosis, meningitis, strokes and the neuromuscular disease myasthenia gravis. According to Bressler, the two most common causes of diplopia in adults older than 50 are thyroid conditions and cranial nerve damage. Diminished blood flow due to diseases such as hypertension or uncontrolled diabetes can damage the cranial nerves. In addition, nerve conditions such as Guillain-Barre syndrome sometimes affect the eyes, causing blurriness or double vision. According to the National Institutes of Health, Guillain-Barre syndrome often follows a minor infection, causing inflammation that damages parts of nerves. Myasthenia gravis is an autoimmune disease that may cause the eye muscle to become too weak to control eye movements. Patients with myasthenia often develop ptosis, or drooping eyes.
Sudden double vision may be an indication of a serious medical condition. According to AllAboutVision.com, double vision may be caused by stroke, head injury, a brain tumor, brain swelling or an aneurysm. Ocular migraines may cause not only headaches but visual disturbances such as double vision. According to AllAboutVision.com, ocular migraines are thought to be due to changes in blood flow in the brain. Accurate diagnosis is critical because the symptoms of ocular migraines may be confused with retinal detachment--a condition that needs immediate treatment to prevent blindness.