Strabismus - Medical experts

Leading Medicine Guide Editors
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Leading Medicine Guide Editors

The medical term strabismus is commonly used to refer to strabismus. It is an imbalance of the eye muscles. It is characterized by the deviation of the visual axes of both eyes from each other. The eyes therefore look in different directions due to a misalignment.

ICD codes for this diseases: H49, H50

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Article overview

What is strabismus?

Normally , the visual axes run parallel in distance vision. When looking at an object that is closer to the eyes, the visual axis runs evenly inwards. With strabismus, however, one eye is turned more inwards than the other.

There is a wide range in the extent of strabismus: from so-called silver vision with barely perceptible deviation of the visual axis to disfiguring , drastic strabismus. The transitions are fluid.

What forms of strabismus are there?

Doctors differentiate between the forms of strabismus according to various criteria:

Types of strabismus

Doctors initially differentiate between two types of strabismus:

  • Primary strabismus: occurs without another eye condition.
  • Secondary strabismus: strabismus is caused by another disease.

The clinical appearance serves as a further distinguishing criterion to define the type.

  • In manifest strabismus (concomitant strabismus), the directions of gaze of both eyes constantly deviate from each other.
  • Latent strabismus (heterophoria) is often just a symptom of overstraining.

Latent strabismus (heterophoria) occurs most frequently. This misalignment usually remains untreated, as it often only occurs when the eye is strained. In most cases, however, the brain is still able to compensate for the strabismus due to the minor disorder. Only ten percent of people with latent strabismus suffer from impairments.

Strabismus concomitans(concomitant strabismus) and strabismus paralyticus(paralytic strabismus), on the other hand, are treated medically. Concomitant strabismus often occurs in infancy or childhood.

Paralytic strabismus is caused by paralysis of the eye muscles, usually due to a previous inflammation or injury.

Strabismus direction

Doctors differentiate between

  • Inward strabismus (strabismus convergens or esotropia), in which one eye is directed towards the nose
  • Outward strabismus (strabismus divergens or exotropia)
Nach innen gerichteter StrabismusInward strabismus @ Alessandro Grandini /AdobeStock

    In addition to the usual horizontal deviations of the visual axis, there are also vertical deviations. The generic term for this form is verticalotropia. If the right eye is higher than the left, doctors speak of hypertropia. If the left eye is higher than the right, it is called hypotropia.

    With the help of strabismus therapy, the patient can often regain the normal eye position. This is necessary in order to merge the two visual impressions of the eyes into a single image (fusion), which is what makes spatial vision possible in the first place. Those affected, however, often see double images.

    Squinting infants often suppress stereotypical vision by using only one eye. In these cases, strabismus can develop into a further visual impairment.

    This is why it is important to check toddlers and babies to see if they have strabismus. So that treatment can be initiated as early as possible.

    Frequency of strabismus

    The different forms of strabismus occur with varying frequency. Heterophoria (latent strabismus) occurs in over 70 percent of all people. It usually occurs when the eyes are overtired or under the influence of alcohol.

    In contrast, strabismus concomitans (concomitant strabismus) occurs in the first two years of life. It is also possible for children to be born with strabismus.

    Around four percent of all children are affected, mostly by early childhood inward strabismus. This form of strabismus usually occurs in babies within the first six months of life. The so-called paralytic strabismus, on the other hand, can affect children, babies and adults alike.

    Causes of strabismus

    Various causes can be responsible for strabismus.

    • The forms strabismus concomitans (concomitant strabismus) and heterophoria (latent strabismus) are due to a disturbed balance of the eye muscles. The actual cause is usually unknown.
    • People who suffer from strabismus concomitans usually have relatives who also suffer from it. This is often accompanied by short-sightedness or long-sightedness.
    • In latent strabismus, on the other hand, the imbalance in the eye muscles only occurs for a short time. This is usually due to the fact that the ability to fuse visual impressions is underdeveloped. In this case, strabismus only occurs with fatigue, the influence of alcohol or other overload factors.
    • Strabismus paralyticus (paralytic strabismus), on the other hand, is caused by paralysis of the outer eye muscles. This form can occur suddenly.

    Possible causes are

    • Muscle disease
    • inflammation
    • tumor
    • Circulatory disorders

    Affected children have often suffered injuries to the face, brain or eye area during birth.

    Symptoms of strabismus

    Strabismus is characterized by the misalignment of the eyes. This causes the eyes to look in different directions. This results in the typical squint.

    The cause is usually that one of the two eye axes deviates from the normal position (parallel position). Most frequently, the position changes inwards or outwards.

    Strabismus is often accompanied by other symptoms:

    • Burning or trembling eyes
    • Concentration problems
    • Increased sensitivity to light
    • Headaches
    • Tilting of the head
    • Blinking or squinting
    • Difficulty reading
    • Clumsiness when grasping objects

    If these signs occur unexpectedly, they can also indicate a later strabismus.

    The different symptoms of strabismus also depend on the particular form of strabismus:

    Heterophoria (latent strabismus)

    Heterophoria or latent strabismus is when the eye muscles are not in balance with each other. However, the brain can compensate for this and ensures that the two visual impressions merge.

    Squinting of the eyes is therefore often not noticeable. Strabismus only occurs due to unfavorable factors such as fatigue, stress, alcohol, mental stress or a general illness.

    Accompanying symptoms occur in around ten percent of those affected:

    • Headaches
    • Rapid fatigue
    • Blurred vision
    • Double vision

    Strabismus concomitans (concomitant strabismus)

    With strabismus concomitans, the so-called concomitant strabismus, it is not possible for the person affected to compensate for the imbalance of the eye muscles on their own.

    The visual axes of both eyes do not automatically focus on the same object. The different angle of vision remains even when the eyes are moved.

    However, the deviation can be so slight that there are no visible symptoms at first and the typical strabismus is absent. This is why doctors sometimes recognize concomitant strabismus late or not at all.

    Strabismus concomitans is often accompanied by slight farsightedness. If the strabismus only occurs in one eye, this eye may also suffer from amblyopia.

    In this form, the affected person may also hold their head at an angle or their eyes may tremble.

    Strabismus paralyticus (paralytic strabismus)

    In this form of strabismus, one or more of the outer muscles of the eye fail. Depending on the direction of gaze, the squinting angle also changes. Due to the sudden onset of strabismus, the affected person usually notices the symptoms suddenly.

    The perception of double vision is typical of this form of strabismus. It is usually the direction in which the eye is directed when the muscle is intact. Strabismus is often accompanied by dizziness and even nausea. To compensate for the double vision, many sufferers hold their head at an angle (compensatory head tilt).

    Progression of strabismus

    Strabismus can often be controlled with early treatment. However, if strabismus concomitans (concomitant strabismus) in a small child is not treated in time, this can leadto visual impairment in the long term. This can no longer be reversed by the time the child reaches school age.

    It is therefore important to have children examined at pre-school age. The earlier doctors diagnose strabismus, the better. The first treatment measures to treat strabismus can be taken as early as six months of age.

    Diagnosis of strabismus

    Strabismus is often already obvious: the typical eye position leads to a clear diagnosis. However, the accompanying symptoms mentioned can also give the doctor a clue. If children are affected, the pediatrician often discovers the misalignment during the regular U1 to U9 examinations.

    Various eye tests and orthoptic tests are available to diagnose strabismus:

    A very important test is the cover and uncover test.

    In the cover test, the child must first cover one eye. It is then checked whether the position of the uncovered eye changes or remains the same. If the eye readjusts, strabismus concomitans (concomitant strabismus) may be present.

    The uncovered eye test, on the other hand, checks whether the uncovered eye attempts to bring about a fusion of the visual images through additional movements. In this case, heterophoria, a latent strabismus, may be present.

    Ultimately, all tests help the ophthalmologist to narrow down the form of strabismus and rule out other diseases. Only once an exact diagnosis has been made is it possible to initiate the appropriate treatment.

    Treatment of strabismus

    In the case of strabismus in childhood or infancy, which doctors recognize at an early stage, conservative treatment is usually sufficient. Children are often spared an operation.

    Conservative treatment for children

    As a rule, the treating doctor prescribes glasses and eye training.

    As part of the fusion training, the children learn how to merge the double images.

    Doctors use occlusion therapy to treat incipient visual impairment. In occlusion therapy, both eyes are alternately covered with a patch. The plaster remains on the eye for a certain period of time. This application forces the weak eye to work harder.

    With this form of therapy, children are able to learn to see well and unlearn to squint. Children with strabismus-related visual impairment are usually treated until they are around twelve years old.

    Okklusionstherapie bei StrabismusOcclusion therapy for strabismus @ kucheruk /AdobeStock

    Conservative treatment for adults

    Adults who suffer from concomitant strabismus also receive therapy to prevent stereo vision and restore full visual acuity.

    If the affected person sees double images, they are often given prism glasses. These have a matt film on one lens. This helps to change the incidence of light rays and avoid stereo vision.

    Adults also often receive fusion training. This form of therapy can cause the eye position to normalize and the strabismus is no longer obvious.

    In the case of strabismus paralyticus, on the other hand, doctors must treat the cause of the eye paralysis.

    In rare cases, the paralysis of the eye muscles can regress without treatment. The problem with this form is that the actual trigger can often not be diagnosed.

    This complicates treatment, which usually depends on the cause. Sometimes the squinting of the eyes persists despite treatment. In such cases, the patient is given prismatic lenses that eliminate the double vision.

    If the strabismus persists for more than six months despite treatment, doctors recommend surgery.

    Surgery for strabismus

    If conservative treatment is not sufficient, surgery is necessary to bring the eyes back into parallel position. Surgery can also be performed for cosmetic reasons or due to emotional stress. In children, the operation is usually performed under general anesthesia; in adults, local anesthesia is often sufficient.

    During strabismussurgery, the surgeon influences the mechanics, mobility and position of the eye. Although this can correct the strabismus, a relapse is possible.

    Prevention

    In general, strabismus cannot be prevented. It is only possible to take prophylactic measures to avoid visual impairment later on. For this reason, you should have the eye position of small children and babies checked. The aim is to start treatment as early as possible.

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