Strabismus: Causes, Risks, Treatment for Children and Adults

Crossed eyes is a vision disorder due to the loss of coordination of both eyes. There is a state of eye deviation when observing the object. Please note, however, that strabismus is not merely an aesthetic issue.

Crossed eyes / squint = strabismus. 
Strabismos - from Greek = to squint. 
Strabos - squinting, squint-eyed. 

As a result of the difference in the axis of the planes of the observed object, double vision occurs. The brain tries to suppress this condition in order to get a correct and sharp final image. Therefore, it ignores the weaker eye. It is an adaptive mechanism of the CNS (central nervous system) = the brain ignores the signal from the weaker eye.

In order for the brain to avoid double vision, it turns off the weaker eye and does not receive any signals or images from it.

A similar effect occurs in lazy eye (the medical term is amblyopia). If it is not detected in young children in time, there will be permanent visual impairment in the affected eye, including blindness.

Squint is a natural cause of amblyopia.

FAQ:

• What causes squinting on one eye?
• What about strabismus in newborns, babies, children and adults?
• What is divergent misalignment?
• How can strabismus be corrected? Do exercises help or is surgery necessary?
• How long does convalescence last after strabismus surgery?

Strabismus may affect young children immediately after birth. However, it may not be permanent in newborns. If it persists in older children, a medical examination is necessary in addition to a screening examination.

In childhood, solutions and remedies are better and have good prospects. Conversely, surgery is unavoidable in adulthood.

Therefore, early and timely treatment is important.
As strabismus is a serious aesthetic problem, it is a psychological burden for both children and adults.
Visual impairment limits the affected person's daily activities.

Strabismus - Medical Terms and a Brief Overview

Strabismus is based on a disorder of visual alignment and coordinated movement of both eyes. It is a pathological condition in which viewing something, that is fixating the axis of vision of both eyes, does not align in one target point.

The position of the eyes is asymmetrical, i.e. uneven.
Orthotropia = binocular alignment with both eyes open. 
Heterophoria = a disorder of the muscular balance of the eyes or also binocular vision. 

Strabismus is classified into several forms. The basic classification is into a primary and a secondary form:

1. Primary
   • latent and manifest
     • manifest form is further classifed into 
       • incomitant (paralytic) -  congenital (inborn) or acquired
       • and comitant (dynamic) - convergent, divergent strabismus, vertical strabismus and special forms of strabismus
     • latent strabismus, found only in certain situations
2. Secondary
3. based on the type of deviation - vertical, horizontal, torsion type
4. according to axial parallelism - comitant (dynamic, in all directions) and incomitant - paralytic with various angles of viewing
5. according to laterality - unilateral / fixed (constant squint in one eye) and alternating, when the fixation alternates between the eyes, with the other eye twitching at that moment

Another classification is based on the direction of gaze:

• Esotropia, where the eyes are crossed, i.e. to the inside - strabismus convergens.

It contains several forms, such as congenital (infantile), acquired, accommodative (refractive esotropia), abnormal accommodative convergence, and ex anopsia esotrope.

• Exotropia, where the eyes diverge, outwardly - strabismus divergens.

There are also several forms, such as basal (constant) - when the child is schooling near and far / intermittent - when looking into the distance / exotropia ex anopsia (the cause is impaired visual function or injury, disease of one eye).

• Heterotropia, the eye is turned cranially, i.e. upwards - strabismus sursumvergens.

• Hypotropia, the eye is turned caudally, i.e. downwards - strabismus deosumvergens.

Table: Some Types of Strabismus with Descriptions

The Eye - A Sensory Organ

We visually perceive up to 90% of information from the environment. The eye is the most important sense. Our eyes allow us to perceive light, colours, shapes, contrast and depth. Thanks to that, we can orient ourselves in the environment.

The eye has a sensory part that captures information from the environment, i.e. light. The motor component is composed of muscles that are important for eye movement.

These oculomotor muscles, along with the oculomotor nerves and the centre of the brain, allow us to move in space.

The eye, or rather the bulbus or the globe of the eye, is about 24 millimeters wide (in adults) and has a spherical shape. Its composition is complex and uses light-sensitive cells, such as suppositories and rods, to perceive light. They transmit visual perception through the optic nerves into the brain from both eyes at the same time.

The perception of the world, its surroundings, space, its depth and overall 3D perception is made possible by the interplay of both eyes.

We direct and fix the view and we perceive it. The brain connects both eyes into one fused image based on the precisely "displayed" images on the retina.

This is called binocular vision.

Vision in Children

After birth, the baby does not perceive the world in colour, as light falls onto the macula peripherally rather than centrally. After week 4, monocular vision begins to develop.

We get binocular vision at about the 3rd month of life.

In children, vision may take about 6-9 years to fully develop.

So, it is during this period that it is important to detect amblyopia and deal with strabismus, so that the brain is able to perceive the world from both eyes instead of allowing the brain to "turn off" one eye.

If the visual centre perceived two different images, the result would be double vision.

Amblyopia cannot be visually deected nor can the child describe it. So, it is necessary for a doctor or a pediatrician to monitor the development and quality of vision. In case of vision impairment, the child's eyes need to be inspected by an eye specialist.

Naopak, škúlenie je viditeľné navonok a dieťaťu spôsobuje výrazné problémy. Hlavne v kolektíve, kde býva terčom výsmechu. Ale výsmešky nie sú konečný problém. Dieťa nedokáže prijať presné informácie z okolia, z čoho plynú ďalšie ťažkosti.

Strabismus occurs in approximately 4-6% of children.

According to the onset, it is classified into:

1. congenital and infantile strabismus - present from birth or within the first 6 months
2. acquired - occurs between the 1st and 3rd year of life, most often than acquired esotropia

Strabismus can be manifest or latent (present only in some situations). It is important to diagnose the condition in children as soon as possible, optimally by 7 years of age.

The reason is the risk of persistent amblyopia and permanent visual impairment.

What is the cause of strabismus? It is a diverse group of conditions. In some cases, there is no clear-cut cause.

Of course, the disease can have multifactorial conditions as the eunderlying cause.

The most common causes of crossed eye/strabismus include:

• eye refractive errors - lack of visual error correction
• eyes with different dioptric error
• unilateral visual acuity impairment (cataract, retinal disease)
• underdeveloped oculomotor muscles
• oculomotor muscle dysfunction
• other congenital diseases of the eye and the ocular orbit (anomalies in size and shape)
• eye diseases such as cataracts, inflammation
• eye and head injuries
• diabetes and other metabolic diseases
• thyroid disorders
• high blood pressure
• degenerative diseases such as multiple sclerosis
• brain diseases
• Down syndrome
• hydrocephalus
• cerebral palsy
• stroke, or thrombosis in the visual centre area of the eye
• inflammation of the brain - encephalitis, meningitis
• tumour - in the brain or the area of the eye
• prematurely born babies
• fetal injury during childbirth or pregnancy
• toxic effects - botulinum toxin, alcoholism

Another classification is based on the cause of oculomotor disorders:

• neurogenic disorder - nerves as the cause
  • disorders of the cranial nerves, their nuclei and pathways
  • in other brain disorders
  • and others
• myogenic disorders - muscle as the cause
  • Graves-Basedow disease - a.k.a. toxic diffuse goiter, is an autoimmune disease that affects the thyroid
  • myasthenia gravis
  • multiple sclerosis
  • and others

Strabismus in newborns, babies and toddlers? 

This condition usually resolves on its own, usually within months without the need for intervention and treatment. The child cannot fix the image with both eyes at once. The eyes change with the gaze, which might cause the eyes to be misaligned at times.

However, if the misalignment lasts longer than 6 months, an examination is necessary (performed by a pediatrician and an ophthalmologist).

Eye misalignment also occurs, for example, in case of illness or, after overcoming it, or during fever.

It is reported that it is mostly a mutual dysfunction of the oculomotor muscles. Various neurogenic causes are also possible.

The manifestations of strabismus are familiar to everyone. This is a condition that is noticeable by others, which is why for many it is an aesthetic issue. However, there are other issues.

As already mentioned, strabismus can be manifest or latent, i.e. only in certain situations. The problem usually occurs in childhood.

In children, it is usually possible to notice that one eye is fixed on the object, while the other one moves to the side, either to the nose, up, down or vice versa, towards the face.

Of course, the acquired form can also occur in adulthood, to the detriment of various conditions, as stated among the causes. Thus, sudden strabismus can be a symptom of another serious illness.

Please note that a sudden onset of crossed eye can be a sign of an acute illness.

Changes in the movement of the eyes towards each other, as if their axes converged, or vice versa, when they diverge in time when looking at the object.

Examples are typical deviations that can determine the form...

Esotropia, Convergent Concomitant Strabismus

The most common type in childhood is the condition when the eye points towards the nose. This is a manifest type in which strabismus is constant.

The eyes may squint alternately.

The main cause in this case is an uncorrected refractive error of the eyes, in the sense of farsightedness.

The error needs to be corrected and the sufferer needs glasses. This can help partially or completely keep the eyes in a parallel position without deviation.

If glasses do not help, one can choose surgery.

Exotropia / Concomitant Divergent Strabismus

In this case, the eyes are directed up towards the forehead. This is a less common type.

The deviation may be the same when gazing at different distances (basal divergent strabismus), but also different. Strabismus may affect one or both eyes.

Strabismus can affect one or both eyes.

Paralytic / Incomitant Strabismus

It covers a wide range of causes, from neurological, through muscular and the like. The deviation is caused by a movement disorder of the oculomotor muscles, in the direction of the damaged muscle.

The eye points to where the problem is.

It is often a paresis (weakening) of the 3rd, 4th or 6th cranial nerve.

What Are the Other Accompanying Symptoms?

In addition to being na aesthetic and psychological issue, strabismus may cause some other issues as well. These result from impaired vision and perception of the surroundings, depth, space and the like.

An example is a child repeatedly bumping into objects or falling down the stairs.

Problems associated with strabismus:

• lazy eye / wall eye, converging ("crossed eye"), diverging eyes, eye movement disorder
• space perception disorder, bumping into objects, problem with walking up stairs
• double vision
• photophobia
• tilting your head when trying to fix your gaze and turning your head, for example when watching TV
• excessively opening one's eyes
• refusal to read
• headache
• dizziness
• vomiting
• painful eyes
• refractive errors, sometimes with large diopters and dioptric difference
• increased overall and eye fatigue

Early diagnosis of the disease is of great importance in protecting the future quality of the child's vision. As neglect and unresolved training leads to amblyopia.

For this reason, regular medical check-ups are important in childhood. Primarily at a general practitioner for children and adolescents, i.e. a pediatrician. In case of a problem, even at a specialist, ie an ophthalmologist.

Of course, the anamnesis is important, ie the difficulties described by man himself. However, young children are not yet able to name their problems.

An eye examination includes, for example:

• strabological examination, which determines the form, position of the eyes, their mobility (motility)
• visual acuity examination, various aids, optometre and the like
• eye movement and deviation test
• examination of the anterior segment of the eye
• ocular background examination

In the acquired form, especially in adulthood, other examinations are also performed (neurological, CT, MRI, EEG, EMG, blood examination, ECG and others, according to associated difficulties).

It is also important to identify risk groups, where it is necessary to pay attention to a thorough examination:

• strabismus in the parents
• refractive errors in parents
• presence of amblyopia of the "lazy eye"
• retinal diseases
• neurological diseases, stroke, high blood pressure, diabetes
• and others

Question: How to get rid of strabismus? Read the section on treatment.