Monocular and binocular diplopia – Double vision
Diplopia, or double vision, most often affects both eyes (binocular diplopia) or, more rarely, one eye (monocular diplopia). This condition indicates a problem with ocular alignment or a disruption in the projection of the image onto the retina. Diplopia is usually diagnosed by an ophthalmologist. However, binocular diplopia most often reflects a neurologically based eye coordination disorder, while monocular diplopia is of ophthalmological origin. In cases of sudden diplopia, cover one eye and then the other to see if the double vision disappears when the right eye, the left eye, or neither is covered. This information will be crucial for the doctor. The underlying cause and treatment are usually performed on an emergency basis.
What is diplopia?
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Diplopia is the medical term for double vision, or seeing double. It is defined as seeing two images of the same object when you look at it.
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It indicates a problem with ocular parallelism or an optical disorder in one eye.
Monocular diplopia and binocular diplopia
Diplopia can be either monocular (one eye) or binocular (both eyes).
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Monocular diplopia occurs when you only use one eye at a time. It may appear as a distorted shadow in the affected eye. The other eye shows no symptoms.
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Binocular diplopia is present when both eyes are open at the same time. It disappears if you cover one of your eyes.
Monocular diplopia is more common and generally less serious. Binocular diplopia is usually caused by a misalignment of the eyes of muscular or neurological origin. Its causes are often more serious.
Horizontal diplopia and vertical diplopia
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If you suffer from binocular diplopia, your double vision may appear vertically (from top to bottom) or horizontally (from side to side).
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The type of diplopia you suffer from depends on the cause of your diplopia and how (or why) your eyes are misaligned.
Who is affected?
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Diplopia can affect anyone, but it is more common in adults over 60 years of age who suffer from diabetes, high blood pressure or who smoke.
Symptoms
In addition to double vision, diplopia can be associated with other symptoms, such as
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Headaches and pain when moving the eye.
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Nausea.
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A feeling of unease.
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Dizziness.
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Blurred or imprecise vision in one or both eyes.
When should you worry about diplopia?
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Go to the emergency room if your double vision does not disappear after 1 hour, or immediately if you experience other symptoms such as pain, dizziness, weakness, slurred speech, or confusion.
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Double vision can be the first sign of a serious problem such as an aneurysm or stroke and you should not ignore it.
Causes of diplopia?
There are many possible causes of diplopia. A distinction must be made between monocular diplopia, which has an ophthalmological cause, and binocular diplopia, which has a neuro-ophthalmological etiology.
Monocular diplopia
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Cataract – Opacification of the lens due to age or trauma.
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Lens or implant dislocation.
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Astigmatism – This is a diplopia that is usually corrected by glasses.
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Keratoconus – Keratoconus is a serious and degenerative astigmatism.
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Dry eye – The syndrome causes refractive errors similar to astigmatism.
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Glasses or contact lenses that are not properly fitted.
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Keratitis and corneal ulcer – The damage results in irregular and fluctuating astigmatism.
Binocular diplopia
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Diabetes – This is the most common cause of binocular diplopia. Hyperglycemia damages the small capillaries that supply blood to the nerves involved in binocular coordination.
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Stroke (CVA) – Ischemic or hemorrhagic lesions damage the oculomotor nerve control centers in the brainstem or cerebellum, resulting in diplopia.
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Hyperthyroidism – In cases of severe exophthalmos related to Graves' disease, oculomotor function may also be affected.
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Myasthenia gravis – In myasthenia gravis, muscle weakness impairs eye coordination. Diplopia is exacerbated by fatigue.
Diplopia and vertigo
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Vertigo is the sensation that the environment around you is spinning. It is usually caused by problems in your inner ear.
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However, if you suffer from severe double vision, you may also experience instability.
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Double vision and vertigo are sometimes symptoms of other problems in your body.
Diagnosis
Differentiating between monocular and binocular diplopia
The first diagnostic step is to differentiate between monocular and binocular diplopia.
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The ophthalmologist covers one eye and then the other.
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If diplopia disappears with alternating occlusion, it is binocular diplopia.
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If diplopia persists in one of the two eyes, it is monocular diplopia.
In cases of monocular diplopia, the assessment will focus on eye examinations:
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Visual acuity
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Examination of the cornea and lens using a slit lamp.
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Fundus examination and OCT to examine the retina.
In cases of binocular diplopia, examinations will be directed according to diagnostic hypotheses:
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Rapid eye movement
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An orthoptic assessment and a Lancaster test – To calculate the extent of the deviation between the two eyes and to identify the muscle or nerve responsible.
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A brain MRI or, failing that, a CT scan in case of suspected stroke.
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Blood test in case of suspicion of Horton's disease or myasthenia gravis.
These tests will provide a comprehensive overview of your problems and point you toward the cause. They will help your doctor identify the origin of the double vision.
Treatment and management
The treatment for diplopia depends on its cause.
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In cases of monocular diplopia, optical correction (glasses or contact lenses) or surgery can restore correct vision.
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In cases of binocular diplopia, treatments are often disappointing. If the deviation remains stable for 3 to 6 months, strabismus surgery may be considered to correct the deficiency and restore ocular parallelism.
How to reduce the symptoms of diplopia?
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The easiest treatment to correct double vision is to cover the affected (or more deviated) eye.
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This can be achieved using an occlusive patch (bandage), an occlusive filter on glasses (Riser) or an opaque lens.
Prevention
There is no way to specifically prevent diplopia, but wearing appropriate optical correction and consulting a doctor in case of abnormal symptoms can help avoid some serious complications.
Here are some tips for eye hygiene.
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Give your eyes a 3-5 minute break every hour by avoiding close-up vision.
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Wear appropriate protective eyewear for all your professional or sporting activities that involve risk.
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Have an eye exam every one or two years (or as often as your ophthalmologist recommends).
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If appropriate: wean yourself off any smoking and manage your diabetes.
Prognosis
Most cases of diplopia are temporary. In fact, your double vision may disappear on its own.
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In the case of myasthenia gravis, the symptoms will return to fatigue.
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In cases of diabetes, paralysis may resolve in 3 to 6 months.
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In the case of cataracts or implant dislocation, the operation will treat the problem.