Esotropia

Esotropia is an oculomotor disorder in which one or both eyeballs are deflected inward. Clinical manifestations of pathology: periodic or permanent displacement of the eye, double vision, violation of stereoscopic and binocular vision. To make a diagnosis, visometry, refractometry, ophthalmoscopy are performed, the nature of vision and the angle of strabismus are determined. Conservative therapy includes pleoptoorthoptic treatment, optical and prismatic correction. With low efficiency, surgical intervention is indicated.

ICD 10

H50 Other forms of strabismus

General information

Esotropia (converging strabismus, converging strabismus) is a disease in which the optical axis of the eyeball deviates from the fixation point in the medial direction. The prevalence of esotropia at the age of 6 months to 6 years is 1-2%. According to statistics, 20% of patients with hypermetropia over +3.5 dpt develop convergent strabismus. About 5% of people with esotropia have mild hypermetropia. Pathology occurs with the same frequency among men and women.

Causes

Acute esotropia occurs in response to an increase in intracranial pressure, which may be a consequence of trauma, intracranial aneurysm, meningitis. Progressive increase of symptoms is observed in multiple sclerosis, myasthenia gravis, Chiari malformation type I. However, in most cases , the following causes of the disease occur:

• Refractive pathologies. Incomplete correction of hypermetropic refraction leads to strabismus. With a high ratio of accommodation convergence to accommodation (AC/A), esotropia becomes constant.
• Violation of vergence. Fibrosis of muscle tissue is the cause of limited mobility of the eyeball. Similar disorders occur when the neuromuscular system is affected against the background of thyroid diseases (hypothyroidism, thyrotoxicosis).
• Visual deprivation. Esotropia is observed when sensory fusion is impossible. This is due to a decrease in the transparency of optical media (corneal cataract, unilateral cataract, vitreous fibrosis) or damage to the retina and optic nerve.
• Duane’s syndrome. This is a genetically determined pathology that develops in patients with a lesion of the SALL4 gene. Autopsy data indicate hypoplasia of the nuclei lying in the area of the Sylvian aqueduct. Atrophy of the abductor nerve is often determined.
• Injury. Fracture of the outer wall of the eye socket, accompanied by damage or compression of the lateral rectus muscle, leads to sudden esotropia. The angle of strabismus increases with bleeding and the growth of hematoma. Its resorption is accompanied by the restoration of the position of the eyes.
• Iatrogenia. Esotropia is a consequence of excessive resection of the medial rectus muscle of the eye. Incorrect transposition of the lateral oculomotor muscle causes strabismus. This complication can be eliminated with repeated intervention.

Pathogenesis

Convergent accommodative strabismus is formed in the presence of hypermetropia above +3.5 dpt. Convergent displacement of the eyeballs is a consequence of the action of accommodation. An increase in the AC/A ratio is characterized by excessive convergence, which also leads to the appearance of symptoms of esotropia. The mechanism of development of non-accommodative strabismus has not been studied.

The pathogenesis of the acute form of the disease is associated with rapidly increasing intracranial hypertension. An increase in the size of the intracranial neoplasm complicates the circulation of intracranial fluid. Mechanical pressure on the oculomotor nerves is accompanied by a deviation of the eyeballs. Similar changes occur during the formation of new foci of demyelination.

Esotropia can be traced in the acute post-traumatic period. This is due to displacement of the bone walls of the orbit or massive intracranial hemorrhage. Reducing the severity of edema and resorption of hematoma contribute to the restoration of the position and mobility of the eyes.

Classification

The disease can be genetically determined (Duane syndrome) or develop sporadically. Setting eye movements in the limit of 5 ° is considered to be the norm, 5-10 ° – microesotropy. An angle of more than 10° should be regarded as converging strabismus. In clinical ophthalmology , esotropia is usually classified into the following forms:

1. Congenital (infantile). A rare type of converging strabismus. Symptoms are diagnosed in the first 6 months of life. At the same time, the child has no signs of central nervous system damage as an etiological factor.

2. Acquired. The severity of the clinical picture reaches its peak after 7 years. Until the appearance of signs of strabismus, the function of binocularity does not suffer. After their detection, vision becomes one-hour or monocular. There are the following options:

• Accommodation. The most favorable form of the disease. Correction of hypermetropia helps to reduce the severity of the angle of strabismus. This is caused by the effect of “diluting” the eyes with a positive sphere.
• Non-accommodative. The first symptoms can be traced after 6 months. Their occurrence is not associated with accommodation and refractive indices of the eyes. The appointment of eyeglass correction does not affect the position of the eyes.
• Sharp. Symptomatology debuts suddenly, without visible prerequisites. The patient clearly indicates the time of manifestation of the first signs. Before the appearance of esotropia, the binocular nature of vision is noted.
• Mechanical. It is a consequence of limited mobility or increased tone of the extraocular muscle. In case of inflammation or injury, the clinic progresses quickly. When the thyroid gland is affected, the dysfunction increases for several years.

3. Secondary. Occurs due to sensory deficiency or the effect of hypercorrection after surgical treatment. Visual deprivation entails esotropia more often in children under 5 years of age.

Symptoms

Esotropia can be observed at any age, but more often the first signs are diagnosed at the age of 6 years. The time of development of the first complaints corresponds to the period when the child begins to be interested in working near. Parents note a constant or periodic deviation of the eye to the nose. Symptoms become more noticeable in the evening, against the background of visual fatigue.

In acute esotropia, complaints related to the underlying disease come to the fore. Patients note the sudden appearance of double vision, which is often accompanied by dizziness and headache. The clinical picture is most pronounced when working at close range. In order to alleviate their condition, patients close one eye.

Convergent strabismus caused by sensory deficiency is characterized by a permanent, more often unilateral deviation of the eye. The severity of the symptoms is the same, both at a close and at a far distance. Concomitant manifestations are vertical deviation and decreased visual acuity. A high degree of anisometropy is characteristic.

Complications

In the absence of timely treatment, the periodic displacement of the eyeball is replaced by a permanent one. Convergent strabismus, which develops due to iatrogenism, in childhood leads to limited mobility of the internal rectus muscle. The most common complication is amblyopia. Loss of binocular and stereoscopic vision is also characteristic. Patients are at risk of abnormal retinal correspondence. In adults, a frequent complication is diplopia.

Diagnostics

During the examination of the patient, it is necessary to collect anamnesis, assess the mobility of the eyes, the ability to converge and divergence. In order to detect latent strabismus, an overlap test (cover-test) is performed. An ophthalmologist studies the position of the eyes when fixing the gaze on an object located at a distance of 40 cm and 6 meters. Objective diagnostic methods:

• Visometry. The study is carried out without correction and with the patient’s glasses. Visual acuity is checked near and far. Vision in the presence of refractive anomalies is often reduced. In the secondary form of the disease, visual functions may correspond to reference values.
• Definition of the nature of vision. The Worth test (four-point test) allows you to establish the monocular, bionocular and simultaneous nature of vision. An alternative is the Bagolini test, the principle of which is based on the raster separation of visual fields.
• Measurement of the angle of strabismus. It is determined by Girshberg or using a synoptophore. The average value varies from 5 to 15°. In rare cases, the indicator reaches 40 prismatic diopters. The angle near may be greater than the distance.
• Computer autorefractometry. Makes it possible to study the type of refraction of the patient. First, a diagnosis is made for a narrow pupil and a trial correction is selected to study the best visual acuity. After achieving cycloplegia, the study is repeated.
• Ophthalmoscopy. Examination of the fundus is an auxiliary diagnostic method, which is carried out with the secondary nature of the disease. With an increase in intracranial pressure, stagnation of the optic nerve disc and dilation of veins are often visualized.

Treatment

Conservative therapy

The treatment regimen is developed individually for each patient, taking into account age, the magnitude of the deviation angle, the presence or absence of the ability to fusion. Regardless of the etiology of the disease, the main goals of therapy are to achieve the correct eye position and binocularity. With concomitant amblyopia, an important step is to increase visual acuity. The complex of therapeutic measures may include:

• Optical correction. In the presence of refractive pathology, the appointment of glasses or contact lenses is indicated. Full correction allows you to form equally clear images on the retina of both eyes. This condition is the starting point in treatment. In case of intolerance, the strength of the lenses is increased in stages (taking into account the patient’s adaptation).
• Prismatic correction. Ophthalmic prisms are used to provide sensory fusion by moving the image closer to the fovea. Their use is justified only if the angle of strabismus does not exceed 10 °. In isolation, prisms are prescribed when diplopia occurs in patients with an acquired form of the disease.
• Pleoptoorthoptic treatment. This type of therapy is used to increase visual acuity, improve the ability to sensory fusion, as well as achieve oculomotor control. Individual exercises are aimed at increasing fusion reserves, developing vergence.

Surgical treatment

Surgical intervention in convergent strabismus is performed if conservative therapy does not allow achieving orthophoria. The leading indication is the angle of more than 15 prismatic diopters in the distance and near when using full optical correction. However, with the accommodative nature of the disease, the operation is contraindicated due to the high risk of inducing secondary divergent strabismus. In case of congenital strabismus, surgical intervention is recommended up to 2 years of age.

Prognosis and prevention

With timely treatment, it is possible to achieve orthophoria, as well as restore visual acuity and binocularity. Convergent strabismus, accompanied by a high degree of amblyopia and anisometropia, is considered unfavorable in prognostic terms. Specific preventive measures have not been developed. Non-specific prevention is aimed at the diagnosis and treatment of refraction and accommodation pathology. If, at the age of 2-3 years, the influence of accommodative effort is leveled, it is possible to prevent the development of strabismus.