Congenital Squint vs Acquired Squint: Differences in Children

Table of Contents

• Understanding Congenital Squint in Infants and Children
• Acquired Squint: Causes and Development in Childhood
• How to Identify Different Types of Childhood Squint
• When Does Squint Typically Appear? Age of Onset Explained
• Diagnostic Approaches for Congenital vs Acquired Strabismus
• Treatment Options: Managing Different Forms of Childhood Squint
• What Are the Long-term Outcomes for Children with Squint?

Understanding Congenital Squint in Infants and Children

Congenital squint, also known as infantile strabismus, refers to eye misalignment that is present at birth or develops within the first six months of life. This condition affects approximately 1-2% of infants and is characterised by a consistent turning of one or both eyes inward (esotropia) or outward (exotropia).

The precise cause of congenital squint remains somewhat elusive, but research suggests it stems from abnormal neuromuscular development affecting the brain’s control over eye muscles. Unlike acquired forms, congenital squint is rarely associated with refractive errors (need for glasses) and typically doesn’t resolve spontaneously without intervention.

A key feature of congenital squint is its persistence. The misalignment remains relatively constant throughout different gaze positions and activities. This distinguishes it from other forms of childhood eye misalignment that may come and go. Additionally, infants with congenital strabismus often develop compensatory head postures to maintain binocular vision or reduce double vision.

Early identification is crucial as congenital squint can significantly impact visual development. Without timely intervention, the brain may suppress vision from the misaligned eye to avoid double vision, potentially leading to amblyopia (lazy eye) and permanent vision impairment. Parents should be vigilant for asymmetric light reflexes in photographs or consistent eye turning, as these may be early indicators warranting prompt ophthalmological assessment.

Acquired Squint: Causes and Development in Childhood

Acquired childhood strabismus develops after the first six months of life in a child who previously had normal eye alignment. Unlike congenital forms, acquired squint often has identifiable triggers or underlying conditions that precipitate the eye misalignment.

The most common form of acquired squint in children is accommodative esotropia, which typically appears between ages 2-4 years. This condition occurs when the eyes turn inward during focusing efforts due to uncorrected hyperopia (long-sightedness). The child’s natural focusing mechanism (accommodation) triggers excessive convergence of the eyes, resulting in a noticeable inward turn.

Other significant causes of acquired squint include:

• Cranial nerve palsies affecting the nerves that control eye muscles
• Orbital trauma or injury disrupting normal eye muscle function
• Certain childhood illnesses including viral infections
• Neurological conditions such as brain tumours or increased intracranial pressure
• Genetic disorders that manifest with progressive strabismus

Acquired squint may develop suddenly or gradually, and its onset pattern often provides valuable diagnostic clues. Sudden-onset strabismus warrants urgent medical attention as it may indicate serious underlying neurological issues. Intermittent squint, where the eye alignment fluctuates between normal and misaligned states, is another common presentation of acquired strabismus that typically worsens during periods of fatigue or illness.

Unlike congenital forms, many types of acquired squint respond well to non-surgical interventions, particularly when the underlying cause can be addressed. Early detection and appropriate management of childhood squint are essential for preserving binocular vision and preventing long-term visual complications.

How to Identify Different Types of Childhood Squint

Identifying the specific type of squint in children requires understanding several key classification systems based on direction, frequency, and underlying cause. Recognising these distinctions is crucial for appropriate management and treatment planning.

The most fundamental classification is based on the direction of eye deviation:

• Esotropia: Inward turning of the eye(s), commonly called “crossed eyes”
• Exotropia: Outward turning of the eye(s), sometimes referred to as “wall-eyed”
• Hypertropia: Upward deviation of one eye
• Hypotropia: Downward deviation of one eye

Based on frequency and consistency, squint can be categorised as:

• Constant: The eye misalignment is present all the time
• Intermittent: The squint appears and disappears under certain conditions, such as during fatigue or illness
• Alternating: The squint switches between eyes, with either eye turning while the other fixates
• Unilateral: Only one specific eye deviates while the other maintains normal alignment

Parents might notice certain telltale signs indicating different types of childhood squint. For esotropia, asymmetric light reflexes in photographs (with the light reflection appearing in different positions in each eye) can be revealing. Children with intermittent exotropia may squint one eye in bright sunlight or demonstrate poor depth perception. Those with accommodative squint might hold reading materials unusually close or demonstrate increased eye turning when focusing on near objects.

Additional identifying features include abnormal head postures (tilting or turning to compensate for vision problems), complaints of double vision (more common in acquired than congenital forms), or closing one eye in bright light. These observations provide valuable diagnostic information for paediatric ophthalmologists assessing childhood eye misalignment.

When Does Squint Typically Appear? Age of Onset Explained

The age at which squint develops provides crucial diagnostic information and often influences both treatment approaches and prognosis. Understanding the typical timeline for different forms of strabismus helps clinicians and parents recognise and address these conditions appropriately.

Congenital or infantile squint typically manifests within the first six months of life. True congenital strabismus present at birth is relatively rare, as newborns normally have variable eye alignment that stabilises within the first few months. Persistent misalignment beyond 3-4 months warrants evaluation. Infantile esotropia, the most common form of congenital squint, typically becomes apparent between 2-4 months of age and is characterised by a large, constant inward deviation.

Accommodative esotropia, the most prevalent form of acquired squint, typically emerges between ages 2-4 years. This timing coincides with increased visual demands as children begin focusing on books, screens, and detailed activities. The squint may initially appear intermittently before becoming more constant without intervention.

Intermittent exotropia often develops between ages 2-6 years. Parents might first notice this outward eye turning when their child is tired, daydreaming, or in bright sunlight. As the condition progresses, the frequency and duration of the deviation typically increase.

Acute-onset strabismus at any age, particularly when accompanied by double vision, requires urgent evaluation as it may indicate serious neurological issues. In older children (7+ years), sudden squint development should raise concerns about potential underlying conditions including cranial nerve palsies, intracranial masses, or inflammatory processes.

The relationship between squint onset age and visual development is significant. Earlier onset generally poses greater risks to binocular vision development, as the critical period for visual pathway formation occurs primarily within the first decade of life, with particular sensitivity in the first few years.

Diagnostic Approaches for Congenital vs Acquired Strabismus

Diagnosing childhood strabismus requires a systematic approach that differs somewhat between congenital and acquired forms. Paediatric ophthalmologists employ specialised techniques to evaluate eye alignment, visual function, and underlying causes, tailoring their assessment to the child’s age and developmental stage.

For suspected congenital squint, diagnostic evaluation typically includes:

• Hirschberg test: Assessing the position of light reflections on each cornea to detect misalignment
• Cover tests: Observing eye movement when covering and uncovering each eye to identify and measure strabismus
• Ocular motility assessment: Evaluating the full range of eye movements in all directions
• Cycloplegic refraction: Using special eye drops to temporarily paralyse focusing muscles for accurate measurement of refractive errors
• Fundus examination: Inspecting the retina and optic nerve to rule out structural abnormalities

For acquired strabismus, additional diagnostic elements often include:

• Detailed history: Identifying potential triggers, timing of onset, and associated symptoms
• Accommodative assessment: Measuring how focusing efforts affect eye alignment
• Sensory testing: Evaluating binocular vision status and presence of suppression or amblyopia
• Neurological examination: Particularly for sudden-onset strabismus to rule out cranial nerve involvement
• Imaging studies: MRI or CT scans may be recommended in cases of acute-onset strabismus without clear cause

Age-appropriate vision testing is essential in both scenarios. For infants, preferential looking tests and fixation preference assessments help evaluate visual function. Older children can undergo more formal visual acuity testing using picture charts or letter recognition.

The diagnostic process also includes assessment for amblyopia (lazy eye), which commonly accompanies childhood strabismus. Early detection of amblyopia is crucial as treatment effectiveness diminishes with age, making prompt and accurate diagnosis of the underlying squint essential for preserving visual potential.

Treatment Options: Managing Different Forms of Childhood Squint

Treatment approaches for childhood squint vary significantly based on classification (congenital versus acquired), underlying cause, age of onset, and presence of associated visual conditions. The primary goals of treatment include achieving proper eye alignment, preserving or restoring binocular vision, and preventing or treating amblyopia.

For congenital squint, treatment typically involves:

• Surgical correction: Often the primary intervention for infantile strabismus, involving adjustment of eye muscle positioning to improve alignment
• Amblyopia management: Including patching of the stronger eye or atropine penalisation to strengthen vision in the weaker eye
• Post-surgical vision therapy: Exercises to enhance binocular function following alignment correction

For acquired forms, particularly accommodative squint, treatment options include:

• Prescription glasses: Often the first-line treatment for accommodative esotropia, correcting hyperopia (long-sightedness) to reduce focusing demands
• Bifocal or multifocal lenses: Sometimes prescribed for children with significant near-point esotropia
• Prism glasses: May help manage smaller angles of deviation or residual misalignment
• Vision therapy: Structured exercises to improve eye coordination and binocular function
• Surgical intervention: Considered when non-surgical approaches are insufficient or inappropriate

For intermittent exotropia, treatment may include:

• Observation: For mild cases with good control
• Orthoptic exercises: To improve control of the deviation
• Patching therapy: Sometimes used to prevent suppression
• Surgery: Recommended when the frequency or magnitude of deviation increases

Treatment timing is crucial, particularly for amblyopia management. The critical period for visual development extends through early childhood, with interventions being most effective when initiated before age 7-8 years. However, individualised treatment plans consider multiple factors beyond age alone.

Regular follow-up assessments are essential regardless of treatment approach, as childhood strabismus can evolve over time. Adjustments to glasses prescriptions, surgical planning, or vision therapy protocols may be necessary as the child grows and visual demands change.

What Are the Long-term Outcomes for Children with Squint?

The long-term outcomes for children with squint vary considerably depending on several key factors including the type of strabismus, age at onset, timing of intervention, treatment compliance, and individual response to therapy. Understanding these potential outcomes helps parents and clinicians set realistic expectations and make informed treatment decisions.

For congenital squint, outcomes typically include:

• Cosmetic improvement: Surgical intervention often achieves satisfactory cosmetic alignment in 60-80% of cases, though some children may require multiple procedures
• Binocular vision: True stereopsis (3D vision) is less commonly achieved with congenital forms, particularly infantile esotropia, though some degree of binocular cooperation may develop
• Visual acuity: With appropriate amblyopia management, good visual acuity can be preserved in both eyes, though subtle differences may persist

For acquired strabismus, particularly accommodative forms, outcomes are generally more favourable:

• Alignment restoration: Many children with accommodative esotropia achieve excellent alignment with appropriate glasses
• Binocular function: Normal or near-normal depth perception can often be preserved if treatment begins promptly
• Potential for outgrowing: Some children with accommodative strabismus may experience reduced dependency on glasses as they age, though many continue to require correction

Long-term follow-up studies indicate that children with successfully treated strabismus generally maintain good visual outcomes into adulthood. However, certain patterns may emerge over time:

• Some children with accommodative esotropia develop non-accommodative components requiring surgical intervention later
• Intermittent exotropia may progressively worsen without intervention, potentially becoming constant
• Recurrence of misalignment can occur years after successful treatment, necessitating ongoing monitoring

Beyond visual outcomes, the psychosocial impact of childhood strabismus warrants consideration. Research suggests that successful alignment correction positively influences self-esteem, social