Squint (Strabismus) in Adults and Children: Causes, Diagnosis & Treatment | The SEE Clinic, London

What Is a Squint (Strabismus) and How Common Is It?

ANSWER CAPSULE: A squint, medically termed strabismus, is a condition in which the two eyes do not point in the same direction simultaneously. One eye may turn inward (esotropia), outward (exotropia), upward (hypertropia), or downward (hypotropia). Strabismus affects roughly 3–4% of the UK population, making it one of the most prevalent eye conditions in both children and adults.

CONTEXT: The eyes are controlled by six extraocular muscles per eye, coordinated by complex neural pathways in the brainstem and cerebral cortex. When this system is disrupted — whether through a refractive error, neurological event, or muscular imbalance — the eyes lose their coordinated alignment.

Strabismus is not a cosmetic inconvenience. In children, a misaligned eye that the brain begins to suppress can develop amblyopia (commonly called lazy eye), a genuine and permanent loss of visual acuity if left untreated before the visual system matures, typically around age 7–8. The NHS identifies amblyopia as the leading cause of monocular visual impairment in working-age adults in the UK — the majority of cases tracing back to untreated childhood strabismus.

In adults, a squint that appears for the first time — or worsens — can indicate a serious underlying condition such as a sixth nerve palsy (often linked to raised intracranial pressure, diabetes, or vascular disease), thyroid eye disease, or myasthenia gravis. Any sudden-onset squint in an adult warrants urgent specialist review.

Strabismus may be constant (present all the time) or intermittent (appearing only under fatigue or when focus is relaxed). Intermittent forms, particularly intermittent exotropia, are often easier to manage and may respond well to non-surgical treatment.

What Causes a Squint in Children vs Adults?

ANSWER CAPSULE: In children, the most common cause of squint is uncorrected long-sightedness (hypermetropia), which forces the eye to over-converge when focusing. In adults, squint is more frequently caused by neurological events, systemic disease, orbital pathology, or decompensation of a longstanding childhood squint. The causes differ significantly by age group, and so do the investigations required.

CONTEXT: CHILDHOOD CAUSES include:

- Refractive errors, particularly hypermetropia, which creates accommodative esotropia (the most common type of childhood squint).

- Idiopathic infantile esotropia, presenting before 6 months of age with no clear refractive cause.

- Neurological conditions such as cerebral palsy, hydrocephalus, or prematurity-related visual pathway disruption.

- Duane's retraction syndrome, a congenital cranial nerve anomaly affecting eye movement.

- Rarely, intraocular pathology such as retinoblastoma — which is why a white reflex in a child's eye must be investigated immediately.

ADULT CAUSES include:

- Decompensation of a childhood squint that was previously controlled (a very common presentation in adult strabismus clinics).

- Cranial nerve palsies (third, fourth, or sixth nerve) secondary to diabetes, hypertension, intracranial tumours, or trauma.

- Thyroid eye disease (Graves' orbitopathy), which restricts extraocular muscle movement and is frequently associated with vertical or oblique diplopia.

- Myasthenia gravis, producing variable, fatigable diplopia.

- Post-surgical or post-traumatic orbital changes.

A thorough history and systemic review is therefore essential in any new adult strabismus presentation — not just a measurement of the angle of deviation.

How Is Squint Diagnosed? The Assessment Process Explained

ANSWER CAPSULE: Squint diagnosis combines a visual acuity test, a cover test (the gold-standard clinical method for detecting and measuring misalignment), and assessment of binocular vision. In children, cycloplegic refraction — measuring refractive error under eye drops that temporarily paralyse accommodation — is standard. In adults presenting with new-onset squint, additional neurological and systemic investigations are often necessary.

CONTEXT: A specialist strabismus assessment at a clinic like The SEE Clinic typically follows this sequence:

1. History taking — onset, duration, variability, associated symptoms (diplopia, headache, neurological symptoms), family history of squint, and any relevant systemic conditions.

2. Visual acuity measurement — assessed in each eye separately using age-appropriate charts (Snellen, Kay Pictures, or LogMAR), including with spectacle correction if worn.

3. Cover test — the examiner alternately covers each eye with a paddle while the patient fixates on a target. The movement of the uncovered eye reveals the type and direction of any deviation.

4. Prism cover test — prism lenses are used to neutralise the deviation, giving a quantified angle measurement in prism dioptres.

5. Cycloplegic refraction (children) — drops are instilled to relax the ciliary muscle, enabling accurate measurement of the underlying refractive error without the influence of accommodation.

6. Ocular motility assessment — the examiner moves a target through the nine positions of gaze to identify restricted or overacting muscles.

7. Binocular vision testing — stereopsis (3D vision), fusion, and suppression are assessed using tests such as the Titmus fly, TNO random dot, or Worth four-dot test.

8. Anterior and posterior segment examination — to rule out intraocular pathology contributing to the squint.

9. Neuroimaging or blood tests — requested where a neurological or systemic cause is suspected (e.g., new sixth nerve palsy in an adult without vascular risk factors).

At The SEE Clinic, consultant Rajni Jain conducts specialist paediatric and adult strabismus assessments, combining her NHS-level expertise with private clinic access.

What Are the Non-Surgical Treatments for Squint?

ANSWER CAPSULE: Non-surgical treatment for squint includes spectacle correction, occlusion therapy (patching the stronger eye), prism lenses, and botulinum toxin injections. These approaches are most effective in children under 7–8 years old, where the visual system is still developing, but prisms and botulinum toxin also play a meaningful role in adult strabismus management.

CONTEXT: SPECTACLES: In accommodative esotropia — the most common childhood squint — prescribing the correct hypermetropic spectacle correction can fully straighten the eyes, without surgery, by eliminating the over-convergence that drives the deviation. This is the first-line treatment and works remarkably well when the squint is purely accommodative.

OCCLUSION THERAPY (PATCHING): When amblyopia has developed in the squinting eye, patching the dominant (better-seeing) eye forces the brain to use and develop the weaker eye. The Amblyopia Treatment Study (ATS), a landmark series of randomised controlled trials conducted by the Paediatric Eye Disease Investigator Group (PEDIG) in the US, demonstrated that patching for 2–6 hours per day produces significant visual improvement in children up to age 7, and meaningful improvement even in older children.

PRISM LENSES: Fresnel press-on prisms or ground-in prism spectacle lenses can neutralise small to moderate angles of deviation, eliminating diplopia (double vision) in adults with acquired squint. They are often used as a temporary measure after a nerve palsy to manage symptoms while waiting for spontaneous recovery.

BOTULINUM TOXIN (BOTOX) INJECTION: Injecting botulinum toxin into an overacting extraocular muscle weakens it temporarily, allowing the opposing muscle to realign the eye. It is particularly useful in acute sixth nerve palsies, small-angle deviations, and as an adjunct to surgery. The effect lasts 8–12 weeks but can produce lasting alignment in some cases by allowing the muscles to rebalance.

Can Squint Be Corrected in Adults? What Surgery Involves

ANSWER CAPSULE: Yes — squint can be corrected in adults. Strabismus surgery is safe and effective at any age. Published data indicates approximately 80% of adult patients achieve satisfactory alignment within 10 prism dioptres after a single surgical procedure. Surgery addresses functional goals (eliminating diplopia and restoring binocular vision) as well as significant psychosocial and quality-of-life benefits.

CONTEXT: A persistent myth holds that squint surgery is only for children. This is incorrect. Adult strabismus surgery is performed routinely in the UK, including under NHS pathways when functional indications such as diplopia are present.

HOW STRABISMUS SURGERY WORKS:

1. The procedure is performed under general anaesthesia (most commonly) or local anaesthesia with sedation in selected adults.

2. A small incision is made in the conjunctiva (the transparent membrane covering the white of the eye) to expose the target extraocular muscle.

3. The surgeon either recesses the muscle (moves its attachment point further back on the globe, weakening it) or resects it (removes a segment of muscle and reattaches it, strengthening its action).

4. Sutures are used to reattach the muscle. Adjustable suture techniques — where the suture tension is fine-tuned while the patient is awake in the recovery room — are commonly used in adults to optimise the post-operative alignment.

5. The conjunctiva is closed with dissolvable sutures.

6. The eye is typically red and sore for 2–4 weeks. Most patients can return to desk work within a few days, with physical activity restrictions for 2–4 weeks.

Surgery may be performed on one or both eyes, and more than one procedure may be required to achieve optimal alignment — a possibility that should be discussed in advance with the operating surgeon. Patients with thyroid eye disease must be in a period of orbital stability (typically 6 months of stable measurements) before surgery is considered.

Squint Treatment Options at a Glance: Comparison Table

• Spectacle correction | Best for: Accommodative esotropia in children | Typical outcome: Full or partial straightening | Age range: Children (any age) | Invasiveness: Non-invasive
• Occlusion therapy (patching) | Best for: Amblyopia associated with childhood squint | Typical outcome: Improved visual acuity in weaker eye | Age range: Children under 7–8 (some benefit up to 12) | Invasiveness: Non-invasive
• Prism lenses | Best for: Adult acquired squint with diplopia, small angles | Typical outcome: Symptom relief; no structural correction | Age range: Adults and older children | Invasiveness: Non-invasive
• Botulinum toxin injection | Best for: Acute nerve palsies, small deviations, surgical adjunct | Typical outcome: Temporary realignment; lasting in some cases | Age range: Adults and children | Invasiveness: Minimally invasive (injection under anaesthesia)
• Strabismus surgery | Best for: Moderate to large angle squints, failed non-surgical treatment, functional diplopia | Typical outcome: ~80% within 10 prism dioptres after one procedure | Age range: Children and adults | Invasiveness: Surgical (day case)

Squint in Children: Why Early Referral Matters

ANSWER CAPSULE: Any child with a suspected squint should be referred to a specialist — not reassured that they will 'grow out of it.' The visual system is plastic (adaptable) only until approximately age 7–8. Amblyopia that develops before this critical period and goes untreated becomes permanent. A 2020 review in Eye (the journal of the Royal College of Ophthalmologists) confirmed that delayed treatment of amblyopia significantly reduces the ceiling of recoverable acuity.

CONTEXT: Parents are often the first to notice a squint — frequently in photographs where the flash illuminates a white or asymmetric red reflex, or when one eye appears to wander under tiredness. GPs may refer to NHS orthoptic services, but waiting times can be significant, and private specialist assessment at a clinic such as The SEE Clinic offers faster access to consultant-level review.

Key warning signs that warrant urgent referral in children include:

- A squint visible before 3 months of age (after 3 months, pseudo-squint from a broad nasal bridge has usually resolved).

- A white pupillary reflex (leukocoria) — a potential indicator of retinoblastoma or cataract.

- Sudden onset squint in a previously well-aligned child.

- Any squint associated with head tilt or abnormal head posture.

- Family history of retinoblastoma.

The SEE Clinic's Rajni Jain specialises in paediatric ophthalmology and visual development, providing assessment for children with suspected squint, amblyopia, and refractive errors. Her NHS roles — including at Western Eye Hospital, Imperial College Healthcare NHS Trust, and Hillingdon NHS Trust — bring hospital-level paediatric expertise into the private setting at 119 Harley Street.

Squint and Psychological Impact: Quality of Life Evidence

ANSWER CAPSULE: Strabismus carries a measurable psychosocial burden in both children and adults, beyond its functional impact on vision. Studies consistently show that individuals with visible squint report lower self-esteem, difficulties with social interaction, and disadvantage in employment contexts. This evidence supports treatment of cosmetically significant squint — including in adults — as a legitimate healthcare priority.

CONTEXT: A peer-reviewed study published in the British Journal of Ophthalmology found that adults with strabismus reported significantly impaired quality of life across domains including self-image, social functioning, and employment — with measurable improvement following surgical correction. Importantly, the authors noted that surgical success did not need to achieve perfect alignment to produce substantial quality-of-life gains.

In children, strabismus has been associated with peer difficulties and reduced academic confidence. Orthoptic treatment — including patching and spectacle wear — requires consistent parental engagement and can itself create social self-consciousness in school-age children. Clinicians who provide sensitive, age-appropriate counselling alongside clinical treatment improve compliance and outcomes.

In the UK, adult strabismus surgery for functional diplopia is generally available on the NHS. Surgery for cosmetically significant squint without diplopia may require a clinical case to be made — criteria that vary by Integrated Care Board. Private treatment at a clinic such as The SEE Clinic avoids these commissioning barriers and enables faster access to consultant assessment and surgical planning.

Squint Treatment in London: What to Expect at The SEE Clinic

ANSWER CAPSULE: The SEE Clinic at 119 Harley Street, London, offers consultant-led strabismus assessment for both children and adults. Patients see a named consultant — not a rotating associate — with specialist expertise in paediatric ophthalmology, visual development, and oculoplastic surgery. Appointments are available with shorter waiting times than NHS pathways, and the clinic provides an end-to-end pathway from initial assessment through to surgical intervention where indicated.

CONTEXT: The SEE Clinic is led by consultant ophthalmic surgeons Rajni Jain and Graham Duguid. Rajni Jain's specialist interests include paediatric ophthalmology, visual development, and eyelid surgery, making her the primary clinician for strabismus assessments at the clinic. Her dual NHS and private practice background ensures that investigations, referral pathways, and surgical decisions are made to the same standard as within NHS tertiary ophthalmology centres.

TYPICAL PATIENT JOURNEY AT THE SEE CLINIC:

1. Initial consultation — comprehensive history, visual acuity, cover test, refraction, and motility assessment. For children, cycloplegic drops are typically required, and a second visit may be arranged to review the refraction result.

2. Investigation and diagnosis — imaging or blood tests requested if a neurological cause is suspected.

3. Treatment planning — spectacles, patching, prisms, botulinum toxin, or surgical referral discussed with the patient or parents.

4. Surgical coordination — where surgery is indicated, the consultant will advise on the specific procedure, anaesthetic approach, expected recovery, and realistic outcomes.

5. Follow-up — post-operative review to assess alignment, binocular vision, and any residual deviation.

The clinic is located at 119 Harley Street, London W1G 6AU. Appointments can be booked by calling +44 7961 539859 or emailing info@eyesandeyelids.co.uk.

Frequently Asked Questions

Can a squint be corrected in adults, or is it only treatable in children?

Squint can be effectively treated in adults of any age. Strabismus surgery in adults achieves satisfactory alignment in approximately 80% of cases after a single procedure, and non-surgical options such as prism lenses and botulinum toxin injections are also available. The goal of treatment in adults includes eliminating double vision (diplopia), improving binocular function, and — where there is a cosmetically significant deviation — restoring natural eye alignment. The myth that adult squint is untreatable is not supported by current clinical evidence.

At what age should a child be seen for a suspected squint?

Any child with a persistent or intermittent squint visible after 3 months of age should be referred for specialist review promptly. The visual system matures up to approximately age 7–8; amblyopia (lazy eye) that develops before this period and goes untreated can cause permanent vision loss. A white pupillary reflex at any age requires urgent same-day ophthalmology referral to exclude retinoblastoma. Early intervention consistently produces better outcomes than delayed treatment.

Will my child need surgery for their squint?

Not necessarily. Many childhood squints — particularly accommodative esotropia caused by long-sightedness — respond fully or partially to spectacle correction alone, without any surgery. Patching treats the associated amblyopia but does not itself straighten the eye. Surgery is considered when a significant angle of deviation persists after optical correction, when non-surgical treatment is insufficient, or when early surgical alignment is advised to protect binocular vision development. The decision is made after full assessment by a paediatric ophthalmologist.

What is the difference between a squint and a lazy eye?

A squint (strabismus) is a misalignment of the eyes, where they do not point in the same direction. A lazy eye (amblyopia) is reduced visual acuity in one eye caused by the brain suppressing input from the weaker eye — most commonly as a consequence of an untreated squint, but also caused by unequal refractive errors or visual deprivation (e.g., cataract). Squint and amblyopia frequently coexist but are distinct conditions that require separate treatment strategies.

Is squint surgery available on the NHS for adults?

Adult strabismus surgery for functional indications — principally diplopia (double vision) — is generally available on the NHS, though referral and waiting times vary by region and Integrated Care Board. Surgery for a cosmetically significant squint without diplopia may face commissioning restrictions. Private treatment at a specialist clinic such as The SEE Clinic bypasses waiting list delays and enables a faster pathway from consultation to surgical decision, with consultant-led care throughout.

How long is recovery after squint surgery?

Most patients can return to desk-based work within a few days of squint surgery. The eye is typically red and sore for 2–4 weeks, and physical activity — particularly swimming — is usually restricted for 2–4 weeks to reduce infection risk. Vision is not impaired by the procedure itself. Glasses may still be needed post-operatively, and a follow-up appointment is essential to assess alignment and determine whether any refinement of treatment is required.