What is Diplopia (Double Vision)?
People with double vision, also known as diplopia, often see two of the same image—whether horizontal, vertical, or diagonal—instead of one.
Sometimes, double vision may result from an annoying but harmless condition known as strabismus characterized by misaligned eyes.1
Other times, the disease develops due to severe medical problems such as multiple sclerosis, brain tumor, giant cell arteritis, and myasthenia gravis (weakening of the body's voluntary muscles).2
The Different Types of Diplopia
The two types of double vision include monocular diplopia and binocular diplopia. These form the basis of initial examination during a doctor's visit.
Understanding the kind of diplopia will help determine if the problem results from an issue in the brain or just within the eye.
Monocular diplopia is a double vision experienced in only one eye. Even when the other eye is covered, the double vision persists. Looking in a different direction also does not get rid of the double vision.
As opposed to monocular diplopia, binocular or bilateral double vision affects both eyes and occurs only while both eyes are open. This is what eye care professionals consider to be “true” diplopia (as opposed to monocular diplopia).
The underlying cause of binocular diplopia is eye misalignment, which happens when the muscles around the eye are undeveloped, weak, or infected. This condition can occur when the extraocular muscles that regulate the direction of the eyes' gaze are weak.
It can also occur when the nerves that control the eyes are damaged. In this case, the eyes struggle to focus and track simultaneously.
What Causes Double Vision?
Each eye forms a unique picture of its surroundings. The brain combines the information from each eye and interprets them as a single, distinct image.
Depth of field is created by combining the efforts of both eyes. Double imaging may be caused by damage to the muscles that move the eyes or the nerves that regulate eye movement.
Certain diseases may also impair the muscles that move the eyes, resulting in double vision.
Possible causes of monocular diplopia include:
- Cataract which is prevalent among people above the age of 80 years3
- Issues with cornea shape, such as in the case of keratoconus or surface irregularity4
- Astigmatism (refractive errors)
- Dry eyes whereby blinking becomes itchy and stingy
- Lens dislocation, such as in the case of eye trauma
- Pterygium (thickening of eye mucous membrane)
Possible causes of binocular diplopia include:
- Strabismus (crossed eyes)
- Diabetes (diabetic eyes) can cause nerve damage in the eyes
- Extraocular muscle damage (or damage to the nerves that innervate these muscles) such as in the case of head trauma, stroke, brain tumor, an eye tumor, or multiple sclerosis
- Grave's disease (thyroid eye disease), which may cause thickening or swelling of eye socket muscles
- Myasthenia gravis, which hinders the ability of the eye muscles to work properly
What Causes Temporary Double Vision? Is it Serious?
Temporary double vision is also a possible occurrence but is rarely severe.
Temporary double vision can be caused by:
- Alcohol intoxication
- Some medications for seizures and epilepsy
- Head trauma
- Excessive tiredness
- Strained eyes
When recovering from LASIK or other vision correction surgery, some people suffer from temporary double vision.5
This kind of diplopia usually goes away with time. In some cases, it will need to be addressed with advanced procedures such as laser surgery.
The severity of double vision varies based on the cause. Even though short-term diplopia is not considered an emergency, early treatment is recommended. This is particularly true if the condition manifests after eye damage or infection.
In general, sudden onset of diplopia (particularly binocular) is cause for concern. Seek an eye care professional right away.
Although diplopia is a visual problem, an eye doctor may not be the only kind of doctor to seek treatment from. For example, if you suspect that your double vision is a side effect of a drug you're taking, you should contact the doctor who prescribed it. However, any case of eye trauma should be addressed by an experienced ophthalmologist.
What are the Symptoms of Double Vision?
The primary symptoms of double vision include:
- Having crossed eyes or "wandering eyes"
- Pain when moving the eye
- Droopy eyelids
- Weakness in the eyes
Watch out for the following symptoms in children:6
- Squinting to enhance vision
- Covering one eye with hands
- Unusual head positioning when looking at something
- Flicking the eyes side to side
What are the Complications of Double Vision?
Every cause of double vision has the potential for problems.
Double vision may result from something easy to treat to something more complex, such as a chronic illness.
Because of the altered field of vision, some people with double vision may experience nausea or vertigo.
Others may experience sensitivity to light or sounds, as well as eye strain.
Double vision may be caused by life-threatening conditions, such as infections or brain tumors, although these are uncommon.
Severe eye discomfort, visual alteration, and headaches are common in many instances of diplopia. Any headache that is accompanied by vision changes can be life-threatening and requires urgent medical attention.
How to Tell if You Have Double Vision (Diagnosis)
It's generally easy to distinguish between monocular and binocular double vision.
However, It may be more challenging to determine the cause. Your symptoms and visual experiences will help decide whether or not you have double vision.
When you go to the doctor, they'll note your symptoms and do a few tests to rule out any other visual issues. They will also do a quick test to determine the kind of diplopia you have.
Once you've been diagnosed with diplopia, the search for a cause follows. When searching for the cause, your doctor will do the following:
- Examine your current health status. Your doctor will discuss with you and take stock of the history of your symptoms, your personal health history, and that of your family.
- Conduct a physical exam. A comprehensive physical examination can assist your doctor in determining the cause of your double vision. This examination may include blood tests, vision checks, toxicity tests, blood sugar tests and imaging (CT scan or MRI).
Many instances of double vision resolve on their own. However, medical examination is recommended to keep track of the patient's condition and further establish the level of impairment.7
Some patients may require MRI neuroimaging to identify abnormalities in the orbital, cranial, or central nervous systems (CNS).8
When is Double Vision an Emergency?
If you have double vision or any other significant change in your vision, you should see your eye doctor as soon as possible.
This will ensure accurate testing, diagnosis, and, if necessary, diplopia treatment or referral to another kind of specialist for further assessment.
Short-term instances of diplopia, such as those caused by stress, tiredness, or drunkenness, are generally not a cause for concern.
However, the sudden onset of double vision should never be overlooked. It may be an indication of a life-threatening illness that requires immediate medical attention.
How to Fix Diplopia: Best Treatment Options
Finding the cause of the double vision is the most important step before deciding on the type of treatment appropriate for you.
Common treatment options for double vision include:
- Corrective lenses. The visual issue may be corrected using eyeglasses or customized lenses. Prisms, for example, can be engraved into your eyeglass lenses to adjust your vision. When placed on one or both lenses, press-on prisms assist in realigning the eyes and eliminate temporary double vision. Prism lenses are carved into the eyeglasses in the case of permanent double vision.
- Eye patch or cover. Double vision may be mitigated by covering one eye. While an eye cover may not be a long-term solution, it may help manage double vision until a more permanent solution is found.
- Eye exercises. If strained or weaker eye muscles are the cause of your visual issue, your doctor may recommend exercises to help you restore eye muscle strength. Your vision problems should improve as your muscles strengthen.
- Surgery. Depending on the cause, surgery may be required to address any physical problems. People who have cataracts or other eye disorders will almost certainly need surgery at some point. The surgical procedure to address that issue should also correct any double vision.
- Botulinum toxin (Botox) injections. Botox is injected into the eyes to cause relaxation of the muscles in the case of binocular diplopia.9
What is the Outlook for Double Vision?
People who have double vision do recover completely after some time. Depending on the cause, some patients may recover with minimal therapy. However, others may need more medical attention to deal with the issue.
The double vision and any other symptoms you're experiencing should go away after addressing the underlying cause.
In rare cases, you may require additional therapy, although most diplopia treatments are effective.
Some of the most common causes of double vision, such as cataracts and cranial nerve palsy, may reoccur. Consult with your doctor as soon as it arises so treatment can begin at the earliest stages.
Can You Prevent Double Vision?
You can prevent double vision if you prevent the occurrence of underlying problems.
Here are some tips:
- Managing diabetes. Diabetes patients who stick to their treatment regimens have a reduced risk of developing double vision. People who observe a balanced diet, and exercise regularly are far less likely to develop diabetes-related double vision.
- Prevent cataract development. Wearing sunglasses, quitting smoking, and eating a balanced diet may help keep your eyes healthy and prevent cataracts.
- Soothe dry eyes. Keep your eyes well-lubricated. Also, try to avoid eye strain caused by extended computer usage. This may contribute to dry eyes.
- Prevent head injuries. Wear your seatbelt, helmet, or appropriate protective gear when in risky environments.
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