Esotropia – Types, Causes, Symptoms, and More

What is esotropia?

Esotropia is the inward deviation of one or both the eyes where the misaligned eye turns towards the nose. This common clinical condition can be

• Constant or intermittent
• Unilateral or bilateral
• Congenital or acquired

Types of esotropia

The classification of esotropia depends on the age when a person develops it, its frequency and whether it relates to eye focusing.

Congenital esotropia

Congenital or infantile esotropia is much more prevalent than infantile exotropia. Congenital esotropia becomes apparent shortly after birth, frequently before the age of six months.

In the first few weeks of life, infants have poor eye movement control, but by six months, the child should have complete eye movement control. 

Esotropia in infants can severely hinder the development of normal binocular vision because the child is unable to acquire basic visual abilities like stereopsis from birth. 

Acquired esotropia

Esotropia is referred to as acquired esotropia if it appears later in life. It may be brought on by underlying medical conditions like Diabetes or other eye issues like untreated farsightedness. 

One of the most common symptoms of the condition is double vision. It might make routine tasks challenging. 

Although some people with acquired esotropia may require surgery, most people with this condition can be successfully treated with glasses and vision therapy.

Constant and Intermittent esotropia

Crossed eyes may be constant or intermittent. Intermittent esotropia occurs once in a while and may only be noticeable when looking at close or distant objects or if the affected person is tired or ill. Constant esotropia is always present.

Accommodative esotropia

Accommodative esotropia is a type of intermittent esotropia. Patients with far sightedness can naturally focus their eyes to improve vision, unlike those who are nearsighted (myopia). 

Accommodation is the process of naturally focusing on an image. It frequently involves a slight inward deviation of the eyes. 

Patients with extreme farsightedness tend to overfocus to the point where their eyes begin to turn abnormally inward. 

Bifocals or glasses are usually used to correct this. Accommodating esotropia is one of the most prevalent types of esotropia.

Causes of esotropia

Esotropia is an eye condition in which one or both eyes turn inward and focus on different things due to uncoordinated muscle movements.

• Conditions like cerebral palsy, brain tumours and hydrocephalus
• Limited vision
• Systemic diseases like Diabetes and Hyperthyroidism 
• Premature birth
• Family history of amblyopia (lazy eye), childhood cataracts, strabismus or glaucoma
• Genetic disorder affecting the eye like Down syndrome 
• Vascular problems or a stroke
• Thyroid-related eye disorders like Grave’s disease

Crossed eyes in infants are not always a sign of esotropia. The shape of the nasal bridge or eyelids can also give rise to cross eyes. The misalignment goes away as the child grows. The condition is referred to as Pseudostrabismus.

Symptoms of esotropia

Misaligned eyes

People with esotropia will have one, or both eyes deviated inwards, causing misalignment.

Eyes that can’t move together

Due to deviation, the eyes fail to function together and focus on an object. This creates blurred or double vision.

Constant squinting 

Individuals with esotropia tend to have a convergent squint due to the inward eye movement. Squints can be constant or intermittent.

Depth perception issues

Congenital esotropia typically causes mild to moderate nearsightedness or farsightedness in infants. 

The dysfunction in the binocular vision or how the eyes function together affects the perception of depth, also known as stereopsis.

Tilting 

Patients who have esotropia frequently incline their heads to maintain proper eye alignment. In fact, a head tilt is often the first sign of this issue, and eye turns are unnoticed.

Double vision

A children’s brain usually suppresses one image to prevent a person with esotropia from seeing two images at once. 

The most typical symptom of adult-onset esotropia is double vision. These patients may experience blurred vision or a smaller visual field as a person sees two images of an object when there should only be one.

Risk factors for esotropia

Diabetes

Diabetes poses specific side effects that can impair circulation to the point where the various muscles that aid eye movement become paralysed or palsied. 

The eyes no longer line up properly, and the brain receives two images rather than one (binocular vision) if one muscle or a group of muscles in the eyes malfunction.

Family history

Esotropia is known to run in families. A family history of the condition doesn’t signify that the subsequent generations will experience the same kind of esotropia or similar severity of the condition.

Genetic disorders

Misaligned eyes or strabismus are present in 20 and 60 per cent of people with Down syndrome. Esotropia most frequently occurs in such patients than exotropia.

Hyperthyroidism (overactive thyroid gland)

Hyperthyroidism is an overactive thyroid gland. Research suggests that almost 90% of patients with Hyperthyroidism experience symptoms of thyroid eye disease (TED). In rare cases, individuals with Hypothyroid or even euthyroid experience esotropia. 

Inflammation and subsequent fibrosis, which result in swelling and thickening of the extraocular muscles, cause esotropia. Due to the restriction on eye movement, there may be double vision or other alignment issues.

Neurological disorders

Divergence palsy affects people of all ages and manifests as acute distance esotropia with divergence loss. An eye can turn inward due to neurological conditions, including hydrocephalus and stroke.

Esotropia can also be linked to several neurological conditions, including trauma, brain tumours, subdural hematomas, multiple sclerosis, cerebrovascular disease, secondary syphilis and head trauma.

Premature birth

A PubMed article states that children with a history of premature birth are more likely to have strabismus like esotropia, which may be present in 2 to 5 per cent of young children. The risk of strabismus increases with lower gestational ages at birth or lower birth weights.

Treatments for esotropia

Corrective lenses

Using spectacles with corrective lenses is the primary treatment for esotropia. Bifocals are eyeglasses with two different lenses for near- and far-sighted eyes. 

Either a bisecting line or a D-shaped segment is typically used to distinguish between the lens powers. 

Children with a lazy eye and accommodative esotropia may benefit from wearing bifocals because they have a stronger power in the lower part of the lens, which is used for close-up activities.

Bifocals work to relax the focusing effort to stop the weaker eye from turning inward. For best results, accommodative esotropia patients should always wear their glasses or contact lenses.

Prism lenses 

Prism recommendation for esotropia is due to the fact that the eyes are not looking in the same direction at the same time.

Prisms reposition the images to match the deviated eye position. This facilitates the coordination of the eyes and can lessen or even eliminate double vision. 

In some patients with accommodative esotropia with a small angle of latent esodeviation, prism glasses work as a suitable non-surgical treatment option. 

Vision therapy

Vision therapy is a personalised therapy that retrains the brain and eyes to work together. 

The therapy involves strengthening the muscles surrounding the eyes and improving vision through eye exercises. 

In order to enhance the function of the crossed eye, vision therapy may also entail the patient wearing a patch over the normal eye. 

Surgery to straighten the position 

Esotropia is typically surgically treated in infants, though some adults may also require surgery.

Surgery is the last resort for esotropia though it does not always completely eliminate the need for wearing glasses or contact lenses.

Some people may require surgical treatment to alter the length of the muscles around their eyes.

Conclusion 

Esotropia is the most typical form of eye misalignment or strabismus in infants, which is defined as an inward turning of the eye. Esotropia may be constant or intermittent. 

Though heredity is the most common cause, esotropia is also linked to a number of neurological conditions, genetic disorders and premature birth. 

Corrective lenses in the form of contact lenses or glasses, vision therapy and surgery in rare cases form the treatments for esotropia.

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