Squint (strabismus) and amblyopia

What it is

Squint (strabismus) means the two eyes do not point at the same target — one may turn in, out, up or down. It can be constant or intermittent (tiredness, fever, near or distance). Amblyopia is a developing brain that never received a clear image; even with the right glasses one eye stays weaker. Squint can cause amblyopia and amblyopia can make a squint more obvious. Progress can still occur after age 6; evidence is clearer at about 7–12. In the teens, especially after previous patching, further gain is often smaller. Assess earlier rather than decide at home that a birthday has closed the door.

Common types (labels, not a diagnosis)

Possible causes (only an examination can sort them)

• Refractive: hyperopia can drive accommodative esotropia; a large difference between the eyes can make the brain ignore the blurrier one
• Development: alignment is still settling in infancy; family history is common but not destiny
• Poor vision in one eye: cataract, fundus disease or uncorrected refractive error
• Nerves: VI (limited abduction, esotropia), IV / trochlear (superior oblique, head tilt), III (ptosis, limited movements; the pupil may dilate)
• Orbit and muscle: thyroid eye disease, myasthenia (variable diplopia, often better in the morning), trauma; tumour is uncommon
• Systemic: stroke, raised intracranial pressure, diabetic palsy — imaging is a doctor’s decision
• After surgery: a change in alignment is for review, not self-diagnosis

Symptoms

• A turn, light sensitivity, a head tilt, squinting, covering one eye to see steadily
• Children may not say “double”; they may blink, lose their place when reading, or a parent notices an eye that “sleeps” at times
• New adult double vision that becomes one image when either eye is closed is usually alignment / nerve / muscle — not “just the glasses”
• Pseudo-esotropia: a flat nasal bridge and epicanthic folds can look like a turn; only an exam can tell — do not rule it out at home

Go to A&E now (call 999 if you cannot get there)

• Sudden double vision with ptosis, a dilated pupil, severe headache, vomiting, slurred speech, weakness or reduced consciousness — rule out a third-nerve palsy and other neurological emergencies
• A new squint, double vision or a stuck eye after head or orbital trauma
• A white pupil (leukocoria) at any age: go to A&E now, or same-day dilated exam by an ophthalmologist to exclude retinoblastoma and other causes. Do not wait and watch at home
• New nystagmus that is asymmetric, or with diplopia, severe vertigo or neurological signs: A&E / 999. Known stable, long-standing congenital or infantile nystagmus alone is not automatic “go to A&E now”
• A child’s eye that suddenly turns markedly while the child is unwell — not “ordinary squint”

Same-day ophthalmic assessment (see an ophthalmologist as soon as possible)

• New adult double vision without the red flags above: same-day assessment by an ophthalmologist who can examine the nerves, with dilation and imaging if the doctor decides
• New nystagmus without the emergency red flags above: same-day assessment by an ophthalmologist as soon as possible
• A child’s squint that worsens over days, a constant head tilt, or covering one eye to look
• Known thyroid eye disease or myasthenia with a sudden jump in double vision

Routine clinic is reasonable (do not wait indefinitely)

• A baby whose eyes are still unsteady or turned after about 3–4 months: specialist assessment, usually not the same-day emergency track, but do not wait until school
• Long-standing intermittent exotropia, a mild long-term in-turn, or an abnormal preschool screen
• Follow-up already on patching or glasses

What a doctor may discuss

• Children often need cycloplegic refraction; without dilation hyperopia and accommodative esotropia can be missed
• Glasses, prism; some accommodative esotropia is treated with hyperopic glasses first — not automatic surgery
• Amblyopia: patching the better eye or pharmacological blur (prescription) and scheduled reviews — glasses alone are not the whole plan
• Surgery is one way to align the eyes; amblyopia therapy still continues. This page does not compare success rates
• Adult paralytic squint: find the cause first (nerve, thyroid, myasthenia). Prism or botulinum toxin are classes a doctor may discuss; this page does not promote a product

Parent gaps: pseudo-esotropia, screening timing, patching adherence

The sections below deepen parent education without rewriting the definitions and urgency ladder above. Parents cannot rule out true squint or amblyopia at home; patching hours and pharmacological blur are prescriptions — this site gives no personal dose.

Pseudo-esotropia: it looks like a turn, but still needs an exam

Many Asian toddlers have a flatter nasal bridge and epicanthic folds that hide nasal sclera, so the eyes look turned in. That is pseudo-esotropia (pseudostrabismus); the visual axes may still be aligned.

1. Corneal light reflex: a clinician checks whether the light spots are centred and symmetric. Pseudo often is; true esotropia is not. Cover testing and related exams still matter — a phone selfie is not a substitute
2. Facial features change with growth: a “look of squint” may ease as the bridge rises; that does not mean an exam was never needed
3. “Just pseudo” once still needs vigilance: some children later show true squint or amblyopia. New intermittent turns, a head tilt, covering one eye to look, or an abnormal vision screen → reassess; do not wait indefinitely on an old impression
4. Cycloplegic refraction may still be needed: even when pseudo is suspected, a doctor may dilate to look for hyperopia and exclude accommodative esotropia

Do not teach parents to clear squint with a torch at home; “it does not look turned” also does not exclude amblyopia.

Children’s vision / alignment: qualitative milestones (not a Hong Kong statute timetable)

International paediatric / paediatric-ophthalmology consensus in qualitative form; follow local paediatrics, maternal–child health or ophthalmology advice in practice. This page does not invent month-by-month local percentages or guarantees.

• Do not wait: white pupil; new / asymmetric nystagmus with red flags; post-trauma double vision / a stuck eye; or new adult double vision with neurological red flags → A&E / 999
• A child’s squint that worsens over days, a constant head tilt, or covering one eye to look → same-day / see an ophthalmologist as soon as possible
• Abnormal screen, more frequent intermittent exotropia, or repeated turns noticed by teachers / parents → book specialty care; do not wait indefinitely for the child to “grow out of it”

Patching: adherence matters more than “having heard of a patch”

Amblyopia patching makes the brain use the weaker eye. PEDIG and related work show that, at suitable ages and severities, daily patching as prescribed can improve acuity in the amblyopic eye; poor adherence wastes that chance. Hours, whether to add near activity, and whether to use pharmacological blur are decided only by the prescribing doctor — this site gives no personal dose.

1. Follow written hours and days; do not lengthen to all-day sealing or stop on your own
2. During patching, use near activities the doctor suggests to “work the weak eye”
3. Log adherence (calendar / diary) and bring it to review
4. Skin and mood: ask the doctor about alternatives if tape allergy; talking with school is safer than secretly cutting hours
5. Full-time glasses still matter; “patch only, never glasses” or “glasses only, never review” drifts from common trial designs
6. Pause and seek care for red flags: a sudden clear worsening of squint after patching, a red painful photophobic patched eye, or a sudden drop in the good eye — contact the prescribing doctor at once; do not “add hours to catch up” yourself

• Do not: buy unverified patch products online as treatment; copy doses from parent groups; claim “X weeks of patching will definitely fix it”

Common myths (for parents)