Double vision or diplopia is when you see two images of an object instead of one. Sudden onset of diplopia can often have a serious underlying disease. The less dominant image is called ghost image.
Types
- Horizontal diplopia: Where the two images are located side by side (horizontally).
- Vertical diplopia: Where the images are vertically displaced, that is, one is higher than the other.
- Monocular diplopia: Double vision that persists even when one of the eyes is closed.
- Binocular diplopia: Double vision that is present only when both eyes are open. With one eye closed, there is no diplopia.
Symptoms
Diplopia can occur in isolation or combined with other symptoms. When you struggle with double vision, it may have some associated symptoms:
- Headache
- Nausea
- Dizziness
- Loss of balance
- Eye weakness
- Eye misalignment or squint
- Droopy eyelids or ptosis
- Weakness of face, inability to close eyes
- Eye pain and strain
All these symptoms can be due to an underlying disease. Therefore, if you experience any double vision— with or without any of the other symptoms — please see your eye doctor as soon as possible.
Causes of Double Vision
A transient episode of double vision can happen for many reasons. These include fatigue, convergence insufficiency and alcohol consumption.
However, persistent diplopia can be caused by:
- Neurological causes like Stroke, head injury, brain tumour, brain swelling (increased intracranial pressure) or brain aneurysm. These usually cause binocular diplopia.
- Eye problems. Eye conditions like cataract, convergence insufficiency and even dry eyes can cause diplopia. (Most cases are monocular diplopia)
- Refractive surgery like LASIK may result in transient double vision or ghost images. Diplopia from refractive surgery usually does not persist after a few weeks.
- Cranial nerve paralysis. Double vision also can be caused by paralysis of one or more of the extraocular muscles. These muscles that control the position and coordination of the eyes. This results in squint, and binocular diplopia. Cranial nerve palsies can be caused by several underlying diseases: diabetes, tumour, head injury, infections like meningitis and encephalitis, high blood pressure, and aneurysm.
Diplopia and Strabismus
A complex system of muscles and nerves help us to see a single image. When two eyes are aligned in the same direction, and focus at the same time, we see one image. When this alignment is disturbed, you get a squint (also called strabismus) and may experience double vision.
If you have had strabismus since you were a child , the brain usually adapts by ignoring the information from one eye. This is called suppression of the image, and may cause lazy eye or amblyopia. This also means that there is no diplopia in case of childhood strabismus or squint. Sudden onset squint, on the other hand, almost always causes diplopia.
Treatment of Double Vision
The treatment for double vision is two pronged. One, your eye doctor may work with your neurologist to diagnose, and address the underlying cause of your symptoms. Two, your doctor may offer you surgery, vision therapy, prisms (which are worn with glasses), eye patches or medications.
Usually, your eye doctor will prescribe special glasses with prisms in the lenses to reduce the diplopia. Sometimes, she will ask you to patch one eye while you are doing vision related tasks. She may also advise you to wear special contact lenses for this purpose. This is because nerve palsies often recover over time, and a surgery therefore may be unnecessary.
Important
The sudden onset of diplopia may be the first symptom for a potentially life threatening disease like stroke, brain tumour or aneurysm. You therefore must contact your doctor immediately if you experience double vision suddenly.
