Diplopia: forms, causes and treatment

By Cristiano Antonino On Apr 20, 2023

We speak of Diplopia to indicate the perception by a subject of 2 images of a single object. It can affect only one eye or both and can be transient or permanent

Diplopia can also arise in some particular conditions and occur temporarily for a short time, such as due to strong physical stress, a trauma to the head, substance intoxication, alcohol abuse or after taking of some drugs.

It is therefore necessary to request a medical examination that begins with the detection of vital parameters in search of fever, heart palpitations and / or respiratory failure.

It then continues with a specialist eye and neurological visit to identify the patient’s type of diplopia.

The specialist visit is very important because it happens that diplopia is erroneously attributed to a visual disturbance of a single eye, while more frequently it is caused by an alteration of the mechanisms of eye movements which prevents correct coordination of the two eyes.

The typical symptom of a diplopia condition is double vision

That is, two objects are seen instead of one that can be perceived:

next to each other (horizontal diplopia)
on top of each other (vertical diplopia)
oblique to each other (diagonal diplopia)

The onset of one form rather than another depends on the disease or deficit of the nerve or eye muscle that caused the diplopia.

Diplopia can also be constant, intermittent or transient

In some cases the patient, in addition to complaining of double vision, may experience other symptoms, such as:

eye pain
decline in vision
protrusion of the eyeball
droopy eyelids
tremors
balance disorders
nausea and vomit
mental confusion
sensitivity changes
motility alterations
heachache

Each of these signals can represent an indicator of even serious illnesses and must therefore always be reported to the doctor to allow for a diagnostic evaluation.

Binocular shape

The binocular form of diplopia is the most common and important since it is almost always caused by a neurological cause, which manifests itself only with both eyes open.

The eyeballs are not aligned well with each other (strabismus) and therefore aim at different points and the image appears double.

Among the causes of this form of diplopia are:

central alterations of ocular motility, caused, in the case of the elderly, by cerebral stroke and by demyelinating pathology such as multiple sclerosis in the younger ones (if these are the causes, other neurological symptoms are usually present as well);
peripheral paralysis, multiple or isolated, of the oculomotor cranial nerves caused by ischemic alterations in the course of diabetes and/or hypertension but also by different types of tumors or intracranial aneurysms in the process of rupture (in these cases diplopia may be the only symptom presented by the patient);
all pathologies of the orbit due to inflammation, tumor or in the course of hyperthyroidism (in this case the patient may present with protrusion of the eyeball and reduction of vision due to involvement of the optic nerve);
muscle pathology in the course of myasthenia gravis and various forms of muscular dystrophy (there is a dysfunction of the muscles which initially can affect only the eye muscles but then can extend to the whole body);
decompensation of a squint present from childhood and never identified.

Binocular diplopia disappears when one eye is closed.

Monocular shape

The monocular form of diplopia is present with only one of the two eyes open, as the problem is not related to the correct alignment of the eyes, but to an alteration of only one of the two.

It is never caused by neurological diseases and there is no strabismus, but rather it is always linked to eye alterations that produce a doubling of the image seen by just one eye.

The most frequent causes are high refractive defects, in particular astigmatism, cataracts and maculopathies.

The most common causes of monocular diplopia are:

cataract
problems with the shape of the cornea, such as keratoconus or surface irregularity
uncorrected refractive error, usually astigmatism
corneal scars
dislocation of the lens

In monocular diplopia, the disorder disappears only when the affected eye is closed.

In the monocular form, the risks are exclusively borne by the vision if the cause, for example a maculopathy, is not correctly identified.

Diagnosis

In case of suspected diplopia, it is advisable to contact the ophthalmologist who carries out an ophthalmological examination complete with study of ocular motility, monocular and binocular visual acuity for possible detection of refractive defects and evaluation of ocular diopters and of the posterior segment of the eye.

Other clinical signs evaluated during the visit can be:

a protrusion of one or both eyes
the diameter of the pupils to identify abnormal miosis or mydriasis
the fall of an eyelid

Very often in cases of acute onset diplopia we make use of a neurological investigation supplemented by specific imaging.

The diagnostic process is completely different depending on the form of diplopia identified, since while in the monocular form the eye examination alone is sufficient, in the binocular form it is often necessary to proceed with a neurological evaluation which will then almost always be supplemented by specific diagnostic tests ( MRI, CT, cerebral angiography, electromyography, blood tests).

Patients with monocular diplopia are seen only by an ophthalmologist for evaluation of eye pathology

Patients with unilateral single cranial nerve palsy, with a normal pupillary response to light, and no other symptoms are usually observed without tests for a few weeks, and many cases resolve on their own.

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Ophthalmologic evaluation may be done to monitor the patient and help further define the deficit, particularly for a third nerve palsy, because it may also progress to involve the pupil.

Diplopia in children

Diplopia is usually easy to diagnose in adults, who are cooperative and therefore can describe the eye disorder.

In children, however, diagnosing diplopia can be more complicated, because they may not be able to clearly explain any vision impairment.

During childhood, the brain can quickly adapt to a double vision problem, ignoring or “eliminating” one of the two images and relying more and more on the signals received from the dominant eye.

This condition, called amblyopia, if neglected can lead to permanent reduction of vision in the affected part so it is important to identify it immediately.

How do you know if a child has diplopia? Watch out for him squinting in an attempt to see better, turning his head in an unusual way, or looking sideways rather than forward.

In most cases, however, diplopia in children is treated successfully, provided the condition is identified early.

Cures and treatments

The treatment of diplopia depends on the cause that triggered it: being a consequence of other pathologies, once cured, it disappears with them.

If the diplopia derives from a condition of strabismus, the therapeutic options may be the use of prismatic lenses that move the image by merging it: in fact, these are glasses that divert the image in one or both eyes and can reduce or eliminate the symptom.

In some forms of transient paralytic strabismus, it may be useful to inject small doses of botulinum toxin into the other eye muscles: the botulinum toxins relax the muscles around the eye, allowing it to line up in the right direction.

Finally, for larger deviations and whose stability over time has been ascertained, strabismus surgery can be used, where the action of one or more extraocular muscles will be weakened or strengthened to allow the correct alignment of the eyeballs, restoring the fusion of perceived images.

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