Simply put diplopia is double vision. That means a person sees two images for a single object at the same time. Diplopia is displaced sometimes vertically, other times horizontally and sometimes even diagonally.
How does it happen? Well, it’s simple. There’s no problem with the eyes. The eyes are fully functional but they cannot target the same object. Usually it is because the extraocular muscles (EOMs) function is impaired. It is caused usually by disorders of the cranial nerves, disorders of the neuromuscular junction, mechanical problems and sometimes ingestion of toxins or disorders involving the supranuclear oculomotor pathways.
Diplopia is a disabilitating disorder that might affect a person’s balance and most often it is a sign of a systemic disease.
There are four important types of diplopia: binocular, monocular, temporary and voluntary.
Binocular diplopia is an eye movement disorder that occurs in both eyes. When covering one eye the binocular diplopia it disappears. Binocular diplopia is caused by diabetes, strabismus, trauma to the eye muscles, myasthenia gravis, grave’s disease and damage to nerves controlling the extraocular muscles.
Monocular diplopia is affecting one eye and it continues even when the other eye is covered. It can be caused by astigmatism, cataracts, keratoconus, pterygium, retinal problems, a dislocated lens, dry eye, a mass of swelling in the eyelid.
Temporary diplopia usually is caused by concussions, head injuries or alcohol intoxications. It could also come as a side effect of certain drugs like anti-convulsant (Lamotrigine), dissociative drugs (Dextromethorphan, Ketamine), anti-epileptics (Zonisamide, Phenytoin) and hypnotics (Zolpidem). It could also be caused by tired or strained muscle.
Some can do it voluntarily and uncouple their eyes and have double vision at will.
There’s only one symptom for diplopia, double vision or seeing two images instead of a single object. So, if you see two objects when there is only one in front of you, you have diplopia. But there are still things to determine.
First and for most the doctor has to determine if it is monocular or binocular double vision. Why is it important? Well, it’s important because the doctor has to determine the cause of the diplopia as the treatment depends a lot on the cause.
To determine if it is binocular o monocular the doctor will ask the patient to cover one eye, then the other one. After determining if it is binocular o monocular, the doctor will try to determine the cause and pre-existing conditions that might favor the disorder. To determine which muscles were affected the doctor will ask the patient to look at the doctor’s finger as the doctor will move it up and down left and right.
Then the doctor might use prisms to determine the amount of double vision. Then other tests might be necessary like MRI (magnetic resonance imaging) or CT (computed tomography). It is easier to give a correct diagnosis in adults than children.
When first symptoms are noticed the patient should see a doctor immediately.
Treatment of diplopia focuses on the underlying cause. Most of the times treatment might include prism correction, eye exercises, surgery, wearing an eye patch on alternative eyes or botulinum toxin.
Prevention is possible for certain causes of double vision. For example to avoid head trauma people should wear seatbelt while driving. If the job involves a risk of eye injury or head trauma the workers should wear headgear and protective goggles. People with diabetes can decrease the chances of having diplopia by controlling their blood sugar.