Diplopia: binocular, monocular

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

Epidemiology

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

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

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

Causes of the diplopias

Specialists call such main causes of this disorder of vision, [2] as:

• ophthalmic problems in the form of clouding of the lens (cataract) or vitreous, damage to the retina or iris, corneal anomalies - keratoconus, refractive disorders (particularly uncorrected astigmatism), sometimes dry eye and tear film deficiency, and idiopathic inflammation or tumor of the orbit of the eye;
• Limitation of movement of one or more extraocular (oculomotor) muscles, which ensure movement of the eyeballs and fixation of their position - due to their weakness in myasthenia gravis (miasthenia gravis), as well as due to paresis/paralysis.

Damage to cranial nerves, brainstem and demyelinating diseases (myelitis, multiple sclerosis, Guillain-Barré syndrome) can cause diplopia in lesions of cranial nerves, [3] innervating the muscles of the eye. Diplopia is one of the manifestations of degenerative changes of the CNS - brain stem and basal nuclei - in progressive supranuclear palsy, Parkinson's disease, as well as lesions of the structures of the autonomic nervous system, as in Parino syndrome.

Post-traumatic diplopia - in most cases after a blow to the face, as well as in fracture of the eye socket (ocular fundus) - is associated with damage to the III cranial nerve, resulting in denervation of the inferior rectus oculomotor muscle (m. Rectus inferior).

Diplopia after a stroke - hemorrhagic (intracerebral hemorrhage) or ischemic (cerebral infarction) - appears due to impaired cerebral circulation. Diplopia of vascular genesis develops in cases of granulomatous inflammation of the aorta and its branches - gigantocellular arteritis, as well as intracranial aneurysms.

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 in thyroiditis there is hyperplasia of the tissue of the muscle funnel of the orbit of the eye with exophthalmos.

Deformation of intervertebral discs in the cervical spine and compression of the vertebral artery with narrowing of its lumen and deterioration of trophic nerve tissue is explained by diplopia in cervical osteochondrosis.

Part of alcoholic polyneuropathy is considered alcoholic diplopia; a critical deficiency of thiamine (vitamin B1) in people with chronic alcohol dependence leads to what is known as Wernicke's encephalopathy, in which the brainstem and III 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.

What can diplopia in children be caused by? Primarily due to hidden strabismus - heterophoria, although the misalignment of the gaze at birth or in the first years of life may not be accompanied by doubling, because the developing CNS of the child is able to suppress the image perceived by the deviating eye. There is a risk of vision loss in this eye.

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

• Conjointed strabismus
• Paralytic strabismus

Diplopia is noted in many genetically determined syndromes in children, e.g. Arnold-Chiari syndrome, Duane, Brown syndromes, etc.

In addition, the occurrence of diplopia may be a consequence of damage to brain tissue (subcortical neurons) by 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 injuries with block nerve palsy, increased cerebral pressure, formation of carotid-cavernous junction;
• eye contusions and injuries;
• inflammation of the membranes of the brain (meningitis);
• chronic arterial hypertension (threatening the development of stroke);
• diabetes;
• elevated thyroid hormone levels in thyrotoxicosis or diffuse toxic goiter (basal goiter);
• Shingles (herpes zoster with Varicella zoster virus affecting the ganglia of the cerebral nerves);
• Intracerebral and maxillofacial neoplasms (including cystic neoplasms);
• Anatomical anomalies of the facial skull in congenital (syndromal) dysostoses and ocular manifestations of craniosynostoses.

Pathogenesis

Eye movements move visual stimuli into the central fovea centralis of the yellow spot or macula (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, one should take into account the possibility of nuclear and infranuclear eye movement disorders in lesions of any nerve providing the functions of extraocular muscles:

• oculomotor nerve (III para- nervus oculomotorius), [4]
• block nerve (IV pair - nervus trochlearis), [5]
• of the withdrawing nerve (VI pair - nervus abducens).

They all pass from the brainstem or brain bridge into the subarachnoid space, then converge in the venous blood-filled cavernous sinuses (cavernous sinuses) on the sides of the pituitary gland. From these sinuses, the nerves follow each other into the upper ocular slit, and from it each of them passes to "its" muscle, forming a neuromuscular junction.

Thus, lesions causing double vision may be throughout the entire length of these nerves, including surrounding structures, as well as extraocular muscle abnormalities and neuromuscular junction dysfunction (characteristic of myasthenia gravis). [6]

A key role in the pathogenesis of diplopia is also played by supranuclear eye movement disorders, which arise from lesions above the level of the oculomotor nerve nuclei - in the cerebral cortex, the anterior cortex and the superior tubercle of the midbrain, and the cerebellum. They include tonic gaze deviation, disorders of saccadic (rapid) and smooth pursuit (simultaneous movement of both eyes between phases of gaze fixation). Visual focusing is impaired in diplopia; there is a deficiency of convergence (convergence of the visual axes); a deficiency of divergence (divergence of the visual axes); abnormalities of fusion (bifoveal fusion) - combining visual excitations from the corresponding retinal images into a single visual perception.

The pathogenesis of diplopia is discussed in more detail in the publication - Why double vision and what to do?

Forms

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

Double vision in both eyes - binocular diplopia - occurs when the images received by the two eyes do not fully coincide, shifting relative to each other. Such displacement may occur suddenly as a consequence of vascular damage in stroke, and gradual progression of the pathology is characteristic of compression lesions of 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 oblique (oblique and torsional).

Double vision in the vertical plane - vertical diplopia/diplopia when looking downward - is the result of paralysis or lesion of the block (IV) nerve, which innervates the superior oblique muscle of the eye (m.obliquus superior). It is often observed in myasthenia gravis, hyperthyroidism, neoplasm localized in the orbit of the eye, supranuclear lesions. And in case of trauma to the orbit of the eye, negative pressure in the paranasal sinuses can have a compressive effect on the lower wall of the eye socket, capturing the inferior rectus muscle of the eye, which leads to vertical diplopia with the inability to lift the affected eye up - that is, when looking down. Damage to the diverting (VI) cranial nerve, on the other hand, causes diplopia when looking sideways.

The peculiarity of horizontal diplopia, which affects many patients with Parkinson's disease and multiple sclerosis, is that it appears only after prolonged observation of close objects. The origin of this type of double vision is most often associated with paralysis of the VI nerve and impaired innervation of the lateral rectus muscle (m. Esotropia (convergent strabismus); 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 - lesion of the median nerve bundle located in the brainstem (responsible for coordination of eye movements) and with associated side gaze disorder - internuclear ophthalmoplegia.

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

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

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

In cases where the horizontal axes of the eyes do not coincide, the left and right eye images may "swap" 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 activities (e.g., driving a car, performing precise actions). Of course, the pathologies that cause diplopia have their own complications and consequences.

Diplopia and disability. Severe, uncorrectable double vision in both eyes severely impairs the ability to work and can lead to disability.

Diagnostics of the diplopias

A thorough history and clinical examination of the patient are necessary to diagnose diplopia. A eye examination and ocular motor testing is performed - eye movement examination with the Hess screen test, which allows an objective assessment of the internal and external range of rotation of each eye.

In monocular diplopia, refractometry and occluder test are mandatory.

Other instrumental diagnostics are also used, such as ophthalmoscopy, refractometry, radiography of the eye socket area, magnetic resonance imaging (MRI) of the brain.

The following tests are taken: general blood count, C-reactive protein, thyroid hormone levels, various autoantibodies, etc. The liquor is analyzed and a bacterial examination of the lacrimal fluid and conjunctival smear is performed. Liquor analysis and bacterial examination of lacrimal fluid and conjunctival smear are performed. [7]

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

Treatment of the diplopias

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

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

Botox (botulinum toxin) may be injected into a stronger eye muscle to restore a weakened extraocular muscle. [10]

Kaschenko orthoptic exercises for diplopia are prescribed to help restore the fusional reflex of the eyes; they are described in detail in the publication - Strabismus - Treatment

Appropriate eye drops for diplopia are used for dry eyes. Ophthalek or Emoxipin drops containing methyl ethylpyridinol hydrochloride for diplopia can be prescribed in case of post-traumatic intraocular hemorrhage or acute cerebral circulation disorder in case of stroke.

Surgical treatment is used for cataract removal, advanced keratoconus, retinal damage, macular fibrosis; diplopia surgery is performed to remove a tumor of the orbit of the eye or brain, eye socket fracture, thyroid problems. [11]

More information in the story - Treating 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 of diplopia is individualized and depends entirely on the underlying condition that causes it.