Diplopia: binocular, monocular

A visual impairment in which a person looks at one object and sees two (in the vertical or horizontal plane) is defined as diplopia (from the Greek diploos – double and ops – eye). [ 1 ]

Epidemiology

According to clinical studies, diplopia is binocular in 89% of cases. Giant cell arteritis is the main cause of diplopia in 3-15% of cases.

Diplopia is observed in 50-60% of patients with myasthenia gravis and progressive supranuclear palsy.

In almost 11% of cases of double vision in only one eye, the cause is facial trauma, thyroid disease, or age-related ophthalmological problems. And in almost the same number of patients, this visual disorder occurs due to dysfunction of the higher mechanisms of eye movement control.

Causes diplopias

Experts name the following main causes of this visual disorder [ 2 ]:

• ophthalmological problems in the form of clouding of the lens (cataract) or vitreous body, damage to the retina or iris, corneal abnormalities - keratoconus, refractive errors (in particular, uncorrected astigmatism ), sometimes - dry eyes and tear film deficiency, as well as idiopathic inflammation or tumor of the eye orbit;
• limitation of movement of one or more extraocular (oculomotor) muscles that ensure the mobility of the eyeballs and fixation of their position - due to their weakness in myasthenia gravis, as well as as a result of paresis/paralysis.

Damage to the cranial nerves, brainstem and demyelinating diseases (myelitis, multiple sclerosis, Guillain-Barré syndrome) can cause diplopia when the cranial nerves [ 3 ] that innervate the eye muscles are affected. Diplopia is one of the manifestations of degenerative changes in the central nervous system – the brainstem and basal ganglia – in progressive supranuclear palsy, Parkinson's disease, and damage to the structures of the autonomic nervous system, as in Parinaud's syndrome.

Post-traumatic diplopia – in most cases after a blow to the face, as well as with a fracture of the orbit (orbital fundus) – is associated with damage to the third cranial nerve, which leads to denervation of the inferior rectus muscle (m. rectus inferior).

Due to cerebrovascular accident, diplopia appears after a stroke – hemorrhagic (intracerebral hemorrhage) or ischemic (cerebral infarction). Diplopia of vascular genesis develops in cases of granulomatous inflammation of the aorta and its branches – giant cell arteritis, as well as intracranial aneurysm.

Double vision in diabetes or thyroid problems, such as autoimmune chronic thyroiditis, is considered diplopia in endocrine ophthalmopathy. In the first case, the cause is incomplete paralysis of the oculomotor nerve - diabetic ophthalmoplegia (ophthalmoparesis). And with thyroiditis, hyperplasia of the tissue of the muscular funnel of the eye orbit with exophthalmos is noted.

Diplopia in cervical osteochondrosis is explained by the deformation of the intervertebral discs in the cervical spine and compression of the vertebral artery with narrowing of its lumen and deterioration of the trophism of nerve tissue.

Alcoholic diplopia is considered part of alcoholic polyneuropathy; a critical deficiency of thiamine (vitamin B1) in the body of people with chronic alcohol dependence leads to the so-called Wernicke's encephalopathy, in which the brainstem and the third pair of cerebral nerves are affected.

Diplopia may develop after eye surgery for cataracts, glaucoma, strabismus, or retinal detachment due to damage to the extraocular muscles.

Why can children have diplopia? First of all, due to latent strabismus - heterophoria, although the misalignment of the gaze at birth or in the first years of life may not be accompanied by doubling, since the developing central nervous system of the child is able to suppress the image perceived by the deviating eye. In this case, there is a risk of vision loss in this eye.

Read about when and why strabismus and diplopia are combined in the publications:

• Concomitant strabismus
• Paralytic strabismus

Diplopia is observed in many genetically determined syndromes in children, for example, Arnold-Chiari syndrome, Duane syndrome, Brown syndrome, etc.

In addition, the occurrence of diplopia may be a consequence of damage to brain tissue (subcortical neurons) by the measles virus (Measles morbillivirus), which leads to the development of subacute sclerosing panencephalitis.

Also read – Eye Movement Disorder with Double Vision

Risk factors

Risk factors include:

• craniocerebral trauma with paralysis of the trochlear nerve, increased cerebral pressure, formation of carotid-cavernous fistula;
• bruises and injuries to the eyes;
• inflammation of the membranes of the brain (meningitis);
• chronic arterial hypertension (threatening the development of stroke);
• diabetes mellitus;
• elevated levels of thyroid hormones in thyrotoxicosis or diffuse toxic goiter (Graves' disease);
• shingles (herpes zoster with Varicella zoster virus lesions of the cerebral nerve ganglia);
• intracerebral and maxillofacial neoplasms (including cystic);
• anatomical anomalies of the facial skull in congenital (syndromic) dysostoses and ocular manifestations of craniosynostoses.

Pathogenesis

Eye movements move visual stimuli to the fovea centralis of the macula lutea of the retina and maintain fixation of the fovea centralis on a moving object or during head movements. These movements are provided by the ocular motor system: ocular motor nerves and nuclei in the brainstem, vestibular structures, and extraocular muscles.

When considering the mechanism of diplopia development, it is necessary to take into account the possibility of nuclear and infranuclear eye movement disorders with damage to any nerve that provides the functions of the extraocular muscles:

• oculomotor nerve (III pair – nervus oculomotorius), [ 4 ]
• trochlear nerve (IV pair – nervus trochlearis), [ 5 ]
• abducens nerve (VI pair – nervus abducens).

They all pass from the brainstem or pons into the subarachnoid space, then converge in the venous blood-filled cavernous sinuses on the sides of the pituitary gland. And from these sinuses, the nerves run next to each other into the superior orbital fissure, and from there each of them passes to "its" muscle, forming a neuromuscular junction.

Thus, lesions causing double vision may be present along the entire length of these nerves, including the structures surrounding them, as well as pathologies of the extraocular muscles and dysfunction of the neuromuscular junctions (characteristic of myasthenia). [ 6 ]

A key role in the pathogenesis of diplopia is also played by supranuclear (supranuclear) eye movement disorders that occur with damage above the level of the oculomotor nerve nuclei - in the cerebral cortex, anterior part and superior colliculus of the midbrain, in the cerebellum. They include tonic deviation of gaze, disorders of saccade (fast) and smooth pursuit (simultaneous movement of both eyes between phases of gaze fixation). Focusing of vision in diplopia is impaired; there is a lack of convergence (convergence of the visual axes); lack of divergence (separation of the visual axes); fusion anomalies (bifoveal fusion) - the unification of visual stimuli from the corresponding retinal images into a single visual perception.

The pathogenesis of diplopia is discussed in more detail in the publication – Why do I see double and what should I do?

Forms

There are different types of diplopia. When the visual axes are displaced, double vision disappears when one eye is closed, but in the presence of ophthalmological problems (pathologies of the lens, cornea or retina), monocular diplopia is observed - double vision that occurs when looking with one eye. But when patients with monocular diplopia of any etiology close the affected eye, they see one image.

Double vision in both eyes – binocular diplopia – occurs when the images received by both eyes do not completely coincide, shifting relative to each other. Such a shift can occur suddenly as a result of vascular damage during a stroke, and gradual progression of the pathology is typical for compression damage to any of the cranial oculomotor nerves. In this case, the image stops doubling if a person closes one eye.

Depending on the plane of displacement, diplopia can be vertical, horizontal and inclined (oblique and torsional).

Double vision in the vertical plane – vertical diplopia/diplopia when looking down – is the result of paralysis or damage to the trochlear (IV) nerve, which innervates the superior oblique muscle of the eye (m.obliquus superior). It is often observed in myasthenia, hyperthyroidism, a tumor localized in the orbit of the eye, supranuclear lesions. And in the case of an injury to the orbit of the eye, the negative pressure in the paranasal sinuses can have a compressive effect on the lower wall of the orbit, capturing the inferior rectus muscle of the eye, which leads to vertical diplopia with the inability to raise the affected eye up – that is, when looking down. But damage to the abducens (VI) cranial nerve causes diplopia with lateral gaze.

A characteristic feature of horizontal diplopia, which many patients with Parkinson's disease and multiple sclerosis suffer from, is that it only appears after prolonged observation of closely located objects. The origin of this type of double vision is most often associated with paralysis of the sixth nerve and impaired innervation of the lateral rectus muscle (m. rectus lateralis), leading to esotropia (convergent strabismus); with divergence insufficiency in old age, idiopathic inability to align the eyes when focusing on close objects (convergence insufficiency) in children and adults; with lateral medullary syndrome - damage to the middle nerve bundle located in the brainstem (responsible for the coordination of eye movements) and associated impairment of lateral gaze - internuclear ophthalmoplegia.

Oblique and torsional diplopia (with oblique double vision) is associated with paresis of the superior and inferior rectus muscles and lateral medullary syndrome, primary orbital tumor, oculomotor (III) nerve neuropathy, Parinaud syndrome or Miller-Fisher syndrome. Patients with such diplopia have a head tilt to the opposite side.

Transient diplopia (intermittent) occurs in patients in a state of cataplexy, with alcohol intoxication, use of certain medications; with head injuries, such as concussion. And persistent diplopia (binocular) develops with displacement of the macula or fovea centralis, in patients with isolated damage to the third cranial nerve or decompensated congenital paralysis of the fourth nerve.

Double vision associated with a disorder of fusion – the process of central and peripheral sensory fusion, that is, combining images from each eye into one – is defined as sensory diplopia.

In cases where the horizontal axes of the eyes do not coincide, the images of the left and right eyes may “switch” places, and this is binocular cross diplopia.

Complications and consequences

The main complication of diplopia itself is the discomfort experienced by the patient and the inability to perform many actions (for example, driving a car, performing actions that require precision). Of course, the pathologies that cause diplopia have their own complications and consequences.

Diplopia and disability. Severe, uncorrectable double vision in both eyes seriously reduces work capacity and can lead to disability.

Diagnostics diplopias

To diagnose diplopia, a thorough patient history and clinical examination are necessary. An eye examination and ocular motility testing are performed - an eye movement study with the Hess screen test, which allows an objective assessment of the internal and external range of rotation of each eye.

In case of monocular diplopia, refractometry and occlusion test are mandatory.

Other instrumental diagnostics are also used, in particular, ophthalmoscopy, refractometry, radiography of the eye sockets, magnetic resonance imaging (MRI) of the brain.

The following tests are taken: general blood test, C-reactive protein test, thyroid hormone level test, various autoantibodies test, etc. Cerebrospinal fluid analysis and bacterial culture of tear fluid and conjunctival smear are performed. [ 7 ]

For patients with diplopia, differential diagnosis means looking for a specific cause of the visual disorder.

Treatment diplopias

Treatment of diplopia always depends on its cause. For example, in case of transient binocular double vision associated with convergence insufficiency, diplopia correction with glasses is used; prismatic glasses are used for diplopia: a so-called Fresnel prism is attached to the lens of the glasses – a thin transparent plastic sheet with angular grooves that create a prismatic effect (change the direction of the image entering the eye). [ 8 ], [ 9 ]

An eye patch or glasses with an occlusive lens are used.

To restore a weakened extraocular muscle, Botox (botulinum toxin) can be injected into a stronger eye muscle. [ 10 ]

Orthoptic exercises according to Kashchenko are prescribed for diplopia, which help restore the fusion reflex of the eyes; they are described in detail in the publication - Strabismus - Treatment

The corresponding eye drops for diplopia are used for dry eyes. And drops containing methylethylpyridinol hydrochloride Oftalek or Emoxipin for diplopia can be prescribed in case of post-traumatic intraocular hemorrhage or acute cerebrovascular accident in stroke.

Surgical treatment is used to remove cataracts, in advanced keratoconus, retinal damage, macular fibrosis; surgery for diplopia is performed to remove a tumor of the eye orbit or brain, in case of an eye socket fracture, and in case of problems with the thyroid gland. [ 11 ]

More information in the material - Treatment of double vision

Prevention

Given the wide range of causes and risk factors, it is difficult to prevent diplopia, and in many cases, its prevention is simply impossible. But timely treatment of diseases that lead to this vision problem can give good results.

Forecast

The prognosis for diplopia is individual and depends entirely on the underlying condition that causes it.