Diplopia (Double Vision)
When you look at an object, complex mechanisms in your eyes and brain result in perception of a single image. Light falls on the lens and gets focused on the retina, a photosensitive layer at the back of the eye. Here light is converted into nerve signals, which travel to the brain where it is processed and interpreted. Eye movements are coordinated by nerves that control eye muscles. Inappropriate functioning of any of these structures could lead to double vision or diplopia.
Causes include corneal infections, scars or dryness; improper alignment (squint), cataract (clouding of the lens), diseases that affect the nerves and muscles such as diabetes, Graves’ disease (thyroid deformity), myasthenia gravis (autoimmune disease), and brain conditions such as multiple sclerosis, stroke, tumour, migraine and aneurysm (bulging vessels).
Diplopia may be intermittent or constant or occur while looking in a particular direction. The two images may appear side by side, one on top of the other or mixed. Diplopia may present by itself or with other symptoms such as eye pain, headache, nausea, droopy eyelids or weakness. Narrowing the eyes, squinting or covering one eye may improve vision and is what usually identifies double vision in young children.
Since diplopia can potentially have a serious cause, it is necessary to seek help immediately. To investigate diplopia, your doctor will review your medical history and perform a comprehensive examination, which usually includes eye examinations, blood tests and imaging studies such as a CT or MRI.
Your doctor will identify the cause of diplopia and provide treatment accordingly. Corneal or lens abnormalities may be treated by surgery, laser or corrective lens in the form of glasses, contact lens or implants. Eye exercises may be recommended to strengthen weak eye muscles, which may also require surgery if severe.