Squint in Children (Strabismus): Signs, Causes, Treatment and When to See a Specialist

What causes a squint in children?

The eyes are controlled by six muscles acting in coordination. For both eyes to point in the same direction simultaneously, the brain must continuously send precisely balanced signals to all twelve muscles (six per eye). In a child with a squint, this coordination breaks down — usually because of one or more of the following.

• Refractive error — particularly long-sightedness (hypermetropia). When a long-sighted child focuses to see clearly, extra effort (accommodation) is required. This accommodation is linked to the convergence reflex, which can pull both eyes inward, causing a convergent squint. Glasses to correct the long-sightedness often fully control this type of squint.
• Muscle imbalance — one or more of the extraocular muscles is weaker or stronger than the others, disrupting the balance of pull.
• Neurological causes — a new or sudden squint in a child with no previous history requires prompt investigation to exclude raised intracranial pressure or other neurological conditions.
• Congenital — some squints are present at birth or within the first few months of life (infantile esotropia). These are larger-angle squints that rarely respond to glasses alone and usually require surgery.
• Illness or trauma — squints can develop following general illness, head trauma, or eye surgery.

Types of childhood squint

• Convergent squint (esotropia) — one eye turns inward toward the nose. The most common type in young children. Often associated with long-sightedness.
• Divergent squint (exotropia) — one eye turns outward. More commonly intermittent, noticed when the child is tired, daydreaming or looking at something in the distance.
• Vertical squint (hypertropia/hypotropia) — one eye deviates upward or downward. Less common; often associated with muscle palsy.
• Constant squint — present all the time, regardless of distance or tiredness.
• Intermittent squint — comes and goes. The child may appear to have straight eyes much of the time. Parents often notice it when their child is unwell or tired.
• Latent squint (phoria) — the tendency to squint is present but normally controlled. Only becomes apparent when binocular vision is disrupted (e.g. covering one eye).

The link between squint and lazy eye (amblyopia)

The brain receives an image from each eye and merges them into a single three-dimensional picture. In a child with a squint, the two eyes are pointing in different directions and send conflicting images. To avoid double vision, the brain learns to suppress (ignore) the image from the misaligned eye.

If this suppression continues throughout early childhood — the critical period of visual development, which runs roughly from birth to age 7–8 — the suppressed eye never develops normal visual acuity. This is amblyopia, or 'lazy eye'. The eye itself is structurally normal, but the neural connection between the eye and the brain is underdeveloped.

Amblyopia is much harder to treat once the critical period has closed. This is why early detection and treatment of squint in children is so important — not just for eye alignment, but to protect the visual potential of both eyes.

Diagnosing a squint

If you suspect your child has a squint, the first step is an assessment by an optometrist, who can perform cover testing and measure visual acuity. Children's vision screening is also carried out at school entry (age 4–5) in England.

Referral to a paediatric ophthalmologist is recommended for any child with a confirmed or suspected squint, significant difference in vision between the two eyes, or failure of the school vision screening.

At a specialist assessment, the ophthalmologist will examine visual acuity in each eye separately, perform a cycloplegic refraction (eye drops to relax the focusing muscles and give an accurate glasses prescription), assess ocular alignment with multiple cover tests and prism measurements, and examine the eye under a microscope to exclude structural causes.

Treatment options for childhood squint

Treatment depends on the type and cause of the squint, the degree of any amblyopia, and the child's age. Most children require a combination of approaches.

• Glasses — the first-line treatment for accommodative convergent squints. Full correction of the refractive error relaxes the accommodation-convergence link and may fully straighten the eyes without surgery. Glasses must be worn consistently.
• Patching (occlusion therapy) — used to treat amblyopia. The stronger eye is patched for a prescribed number of hours per day, forcing the brain to use and develop the weaker eye. Patching works best before the end of the critical period (up to approximately age 7–8).
• Atropine drops — an alternative to patching. Atropine is instilled in the stronger eye, blurring its vision and forcing the brain to rely on the weaker eye. May be preferred over patching for younger children or where compliance is poor.
• Surgery — recommended when the squint is not controlled by glasses, when the angle is too large to be corrected by glasses alone, or when a squint persists after amblyopia has been treated. Surgery rebalances the extraocular muscles. It is performed under general anaesthetic and is a day case procedure.
• Botulinum toxin (Botox) — an alternative to surgery in selected cases, particularly for recently acquired squints. Botox is injected into an overacting muscle, temporarily weakening it. The effect lasts 3–4 months. Can also be used diagnostically before surgery.

When should I take my child to see a specialist?

Any child with a squint that is constant, newly developed, or associated with reduced vision should be seen promptly. Children do not grow out of squints — the squint itself may appear to vary with tiredness, but the underlying muscle imbalance does not spontaneously resolve, and the risk of amblyopia is real.

• A constant inward or outward turn of one eye at any age
• An eye that occasionally drifts, especially when tired or unwell
• A child who tilts or turns their head to look at things
• A child squinting in bright sunlight (often a sign of an intermittent exotropia)
• Failed school vision screening
• A family history of squint or glasses in childhood
• A new squint developing rapidly over days or weeks — seek urgent assessment

Can adults be treated for a childhood squint that was never corrected?

Yes — adult squint surgery is available and can be very effective at improving eye alignment even if the squint has been present since childhood. The amblyopia (reduced vision in the affected eye) that may have developed during childhood cannot be reversed in adulthood, but the alignment of the eyes can be significantly improved.

Adult squint surgery is commonly sought for cosmetic reasons, to improve binocular function, or to address double vision. It is performed under local or general anaesthetic and, in adults, the adjustable suture technique can be used to optimise alignment.

Paediatric squint specialist in Yorkshire

Mr Mohamed Mohyudin is a Consultant Ophthalmic Surgeon with subspecialty fellowship training in paediatric ophthalmology and strabismus. He is a substantive NHS Consultant at Calderdale and Huddersfield NHS Foundation Trust and offers private paediatric and adult squint consultations at Spire Elland Hospital, Elland, West Yorkshire.

Private consultations are typically available within 1–2 weeks. No GP referral is required for self-pay patients. To book, call Spire Elland on 01422 324000.