GC123 Eye Problems In Children
Eye problems in children encompass a range of ophthalmological conditions including amblyopia, strabismus, refractive errors, and congenital abnormalities that require early detection and management to prevent permanent visual impairment.
Eye Problems in Children
Lecture Map
This lecture, delivered by Dr. Kendrick Shih for the MBBS V Senior Clerkship, walks through the five most common paediatric ophthalmic presentations in a scenario-based format [1]. The underlying thread is: the paediatric visual system is immature and developing — so any obstruction to clear, focused images reaching the visual cortex during the critical period can cause permanent visual loss (amblyopia) if not detected and treated early. That's why this matters.
- Understand how the visual system develops in children and why that development creates a unique vulnerability window.
- Assess visual acuity in pre-verbal and verbal children using age-appropriate methods.
- Recognize, classify, and manage refractive errors, amblyopia, strabismus, epiphora (tearing), and leukocoria in children.
- Know when to refer urgently (e.g., leukocoria → retinoblastoma) versus manage conservatively (e.g., nasolacrimal duct obstruction).
- Understand the Hong Kong public-health context: Pre-School Vision Screening by the Department of Health at age 4–5 years at MCHCs.
The Fourth Summative commonly tests: the pinhole test rationale, amblyopia definition/types/treatment, cover-test interpretation, leukocoria differential diagnoses (especially retinoblastoma), and congenital nasolacrimal duct obstruction management. Expect MCQs and mini-cases.
Ocular structures are fully present at birth, but not yet mature. [1]
This is the single most important principle in paediatric ophthalmology. The eye is anatomically complete at birth, but both the optics and the neural processing are immature. This creates a critical (sensitive) period during which the brain's visual cortex is "learning" to interpret images. If that learning is disrupted (by blur, occlusion, or misalignment), the cortical connections never form properly → amblyopia.
Axial Length Growth
| Age | Axial Length |
|---|---|
| Birth | 16–17 mm |
| 1 year | 20–21 mm |
| Adult | 23–25 mm |
Why this matters: A shorter eye is relatively hyperopic (farsighted) — the focal point falls behind the retina. As the eye grows, the focal length changes. This process of the eye "growing" toward emmetropia (where the focal point falls exactly on the retina without accommodation) is called emmetropization.
Most neonates and infants are hyperopic. Emmetropization is greatest at age 1–2 years. [1]
- Neonates see blurry images initially.
- They have not yet learned to accommodate (focus using the ciliary muscle).
- The visual pathway from the macula to the visual cortex is immature.
- Hyperopic defocus may actually be the signal that drives normal axial growth (emmetropization) — this is why the lecture includes a "?" before this statement; it's a working hypothesis.
Key Concept: Emmetropization
Think of the neonatal eye as a camera with the wrong lens for its body. The eye grows longer so that the image lands on the sensor (retina). If this process overshoots → myopia. If it doesn't complete → persistent hyperopia. Anything that blocks a clear retinal image during this period disrupts the feedback loop and leads to amblyopia.
2. Visual Acuity Assessment in Children
Visual acuity and binocular visual function (stereoacuity), ocular alignment and movement, refractive error, slit-lamp examination and fundoscopy — these are the key parts of assessment [1].
- Birth: Very poor (~6/120 or worse). Blink reflex to light only.
- 6 weeks: Fixation develops.
- 3 months: Central, steady, maintained (CSM) fixation.
- 6 months: ~6/18–6/36.
- 1 year: ~6/12–6/9.
- 3–5 years: ~6/6–6/9 (near adult levels).
- Full adult acuity (6/6): Usually by age 5–7 years.
| Age Group | Method | Details |
|---|---|---|
| Preverbal ( < 2 yrs) | Pupil response, fixation reflex | Response to light |
| Objection to monocular occlusion | If one eye sees well and you cover it, the child objects. If the child doesn't object to covering one eye, that eye may have poor vision | |
| Hundreds and thousands | Picking up tiny cake decorations from 33 cm (≈ Snellen 6/24) [1] | |
| Preferential looking / grating acuity | LEA Gratings, Teller Acuity Cards, Cardiff Acuity Test. Measured in cycles per degree (cpd). Snellen 6/6 = 30 cpd, 6/60 = 3 cpd [1] | |
| Verbal (2–5 yrs) | Matching / picture tests | Sheridan-Gardiner (matching letter), Kay Pictures, LEA Symbols |
| Older children ( > 5 yrs) | Snellen / LogMAR chart | Standard adult charts |
High Yield: Grating Acuity Overestimates
Grating (resolution) acuity overestimates VA compared to recognition acuity (e.g., Snellen). [1] This is because detecting a pattern of black-and-white stripes is easier than recognizing a specific letter. If you're asked "What is a limitation of preferential looking tests?" — this is the answer.
Fixation reflex — ability to fixate and follow (maintain fixation) a target (e.g., light, small toy) — NOT present at birth. [1]
| Age | Milestone |
|---|---|
| 2–3 weeks | Uniocular pursuit movement of target |
| 6–24 weeks | Binocular pursuit movement of target; convergence (accommodation lags until 24 weeks) |
Clinical pearl: If a child cannot fix and follow by 3 months, this is a red flag for significant visual impairment and warrants urgent ophthalmology referral.
Stereoacuity: Starts at 4 months, peaks at 2 years and well developed by 4 years, slow beyond 4 years and complete by 9 years. [1]
- Tested using Frisby Stereo Tests (graded circles and animals) or Titmus Fly [1].
- Good stereoacuity requires two aligned eyes each with reasonable acuity — it is destroyed by strabismus or amblyopia.
- Clinical relevance: If stereoacuity is poor, suspect strabismus or amblyopia even if monocular VA seems acceptable.
Critical Window for Treatment
The "critical period" for visual development is essentially birth to ~8–9 years. Amblyopia treatment is most effective before age 7 and becomes progressively less effective after age 9. This is why the Hong Kong DH screens at age 4–5 — early enough that intervention can still work.
3. Refractive Errors (Scenario 1)
Scenario 1: A four-year-old girl with poor vision — what are the key parts of assessment? [1]
| Type | Optics | Common in Children? |
|---|---|---|
| Myopia (short-sightedness) | Eye too long / cornea too curved → image focused in front of retina | Increasingly common; Hong Kong has one of the world's highest prevalences |
| Hyperopia (far-sightedness) | Eye too short → image focused behind retina | Physiological in infants/toddlers; should reduce with emmetropization |
| Astigmatism | Cornea/lens not spherical → different focal points in different meridians | Common; often co-exists with myopia or hyperopia |
In children, cycloplegic refraction is essential. [2]
Why: Children have very strong accommodation. Without paralyzing the ciliary muscle (using cyclopentolate 1% or atropine 1%), the child's accommodation will mask the true refractive error — you'll under-measure hyperopia and potentially under-prescribe correction. The exam may ask why atropinized refraction is needed in children — this is the reason.
Treatment: Improve vision AND prevent amblyopia [1]
- Prescription glasses / contact lens — correct the refractive error so a clear image reaches the retina.
- Prevent myopic progression — this is a major public health issue in East Asia:
| Method | Mechanism | Notes |
|---|---|---|
| Low-concentration atropine eye drops (0.01% / 0.05%) | Reduces scleral remodeling (exact mechanism debated; probably acts on non-accommodative muscarinic receptors in the sclera/choroid) | Currently first-line pharmacological myopia control in HK |
| Orthokeratology (Ortho-K) | Rigid contact lens worn overnight reshapes cornea, creating peripheral myopic defocus | Effective but carries risk of microbial keratitis |
| Peripheral (myopic) defocus spectacles | Contact lens or special spectacle lenses (DIMS, HALT) that correct central vision while creating myopic defocus peripherally | Hypothesis: peripheral myopic defocus signals the eye to slow axial growth |
In Hong Kong, the Department of Health arranges for all children aged 4–5 years to undergo vision screening ("Pre-School Vision Screening") at their Maternal and Child Health Centres (MCHCs). [1]
High Yield Exam Point: Pre-School Vision Screening
Know that this is done at age 4–5 at MCHCs in HK. This is a public health measure to detect refractive errors, amblyopia, and strabismus early enough to treat within the critical period. It's part of the broader ICHDP program [3].
4. Amblyopia ("Lazy Eye") (Scenario 2)
Scenario 2: A 4-year-old girl with bilateral myopia, more severe in the right eye. Best-corrected VA (BCVA): 6/24 (right eye), 6/6 (left eye). No squint. Normal slit-lamp and fundus. What is the likely cause for decreased BCVA in the right eye? [1]
Answer: Refractive Amblyopia (most common type of amblyopia) [1]
Amblyopia = reduced visual acuity in one (or both) eyes that cannot be fully corrected with lenses and for which no structural or pathological cause is found on examination. It results from abnormal visual experience during the critical period of visual development.
Why does it happen from first principles? The visual cortex receives inputs from both eyes during development. If one eye consistently sends a blurrier image (due to refractive error, occlusion, or misalignment), the cortex preferentially processes the clearer input and actively suppresses the blurry one. Over time, the cortical connections from the affected eye are pruned → permanent reduction in that eye's visual capacity.
| Type | Mechanism | Example |
|---|---|---|
| Refractive amblyopia (most common) | Unequal refractive error between eyes (anisometropia) → one eye consistently blurred | Scenario 2: right eye more myopic |
| Strabismic amblyopia | Misaligned eye suppressed by cortex to avoid diplopia | Scenario 3: convergent right eye |
| Stimulus-deprivation (occlusion) amblyopia | Physical obstruction prevents light/images reaching retina | Complete ptosis, corneal opacity, congenital cataract [1] |
| Bilateral refractive amblyopia | High bilateral refractive error (both eyes blur equally) → bilateral amblyopia | High bilateral hyperopia or astigmatism |
High Yield: Causes of Stimulus-Deprivation Amblyopia
Complete ptosis, corneal opacity, congenital cataract — memorize this triad from the lecture slides [1]. These require urgent treatment because deprivation amblyopia is the most severe and hardest to reverse.
Correct underlying cause → Correct any refractive error → Occlusion therapy (patching) [1]
| Step | Rationale |
|---|---|
| 1. Treat the underlying cause | Remove cataract, lift ptosis, etc. — eliminate the physical barrier |
| 2. Correct refractive error | Glasses to ensure the clearest possible image reaches the retina |
| 3. Occlusion therapy (patching) | Patch the good eye to force the brain to use (and develop connections for) the amblyopic eye |
- Patching is dose-dependent: more hours/day → faster improvement, but also more distress for child and family.
- Alternatives to patching: atropine penalization (blur the good eye pharmacologically with atropine drops — dilates pupil + paralyzes accommodation → blurs near vision in the good eye).
- Critical: Treatment is time-sensitive. Best results if started before age 7; some benefit up to ~10–12 years; essentially no benefit after teens.
5. Strabismus (Squint) (Scenario 3)
Scenario 3: A 4-year-old boy with VA 6/24 (right), 6/6 (left). Right eye convergent on exam, slowly taking up fixation when left eye is covered. Refraction: right > left hypermetropia. Normal fundus. [1]
When the eyes are misaligned, the brain receives two different images. In adults, this causes diplopia (double vision). In children, the brain has a powerful adaptive mechanism: it suppresses the image from the deviating eye to avoid confusion. This is good for comfort but terrible for development — it leads to strabismic amblyopia in the suppressed eye.
Visual suppression of deviating eye → Because of visual suppression [children don't get diplopia, but they get amblyopia instead] [1]
| Feature | Categories |
|---|---|
| Direction | Esotropia (convergent / inward), Exotropia (divergent / outward), Hypertropia (upward), Hypotropia (downward) |
| Manifest vs Latent | Heterotropia (manifest — present all the time), Heterophoria (latent — only appears when fusion is disrupted, e.g., by covering one eye) [1] |
| Comitant vs Incomitant | Comitant: angle of deviation same in all directions of gaze (typically childhood esotropia). Incomitant: angle varies with gaze direction (typically cranial nerve palsy) |
Corneal light reflex (Hirschberg test), Cover test (heterotropia), Uncover test (heterophoria), All stereoacuity tests [1]
| Test | What It Detects | How It Works |
|---|---|---|
| Hirschberg test (corneal light reflex) | Manifest strabismus | Shine a light at both eyes; note the position of the corneal reflection. If centered in both pupils → normal. If displaced → strabismus. Each mm displacement ≈ 7° of deviation [1] |
| Cover test | Heterotropia (manifest squint) | Cover the fixing eye → watch the uncovered eye. If it moves to take up fixation → it was deviated → heterotropia [1] |
| Uncover test | Heterophoria (latent squint) | Cover one eye (break fusion) → watch that same eye as you uncover it. If it drifts and then re-fixates → latent deviation (heterophoria) [1] |
| Stereoacuity tests | Indirectly detects misalignment | Ocular misalignment precludes good stereoacuity [1] |
Exam Trap: Cover Test vs Uncover Test
Students often confuse these. In the cover test, you watch the other (uncovered) eye move. In the uncover test, you watch the same eye you just uncovered. Cover test detects manifest squint. Uncover test detects latent squint.
Fully Accommodative Esotropia: Full correction of hypermetropia with glasses eliminates the accommodative drive, which is linked with convergence (accommodation-convergence reflex). [1]
From first principles:
- The child is hyperopic → to see clearly, the child must accommodate (increase lens power).
- Accommodation is neurally linked to convergence (the eyes turn inward together) — this is the accommodation-convergence reflex.
- Excessive accommodation (as in uncorrected hyperopia) → excessive convergence → esotropia.
- Fix: Prescribe full hyperopic correction → less accommodation needed → less convergence → eyes straighten.
Right eye refractive (anisometropic) / strabismic amblyopia [1] — In this scenario the right eye has both mechanisms causing amblyopia: it is more hyperopic AND it is the deviating eye.
Management: Occlusion therapy (patching of normal eye → left eye). Consider squint surgery if develops Partially Accommodative Esotropia. [1]
| Type | Definition | Management |
|---|---|---|
| Fully accommodative esotropia | Squint fully corrected by glasses alone | Glasses ± patching for amblyopia |
| Partially accommodative esotropia | Squint reduced but not eliminated by glasses | Glasses + squint surgery for residual deviation |
| Non-accommodative esotropia | No improvement with glasses | Squint surgery |
6. Epiphora / Tearing (Scenario 4)
Scenario 4: A one-month-old boy with tears overflowing from both eyes since birth. [1]
Mechanism: The nasolacrimal duct (NLD) drains tears from the eye into the nose. In ~30% of neonates, the lower end of the NLD (at the valve of Hasner) is still blocked by a thin membrane at birth. This causes tear overflow (epiphora), often with mucoid discharge and crusting.
Why it usually resolves: The membrane typically opens spontaneously in the first 12 months of life as the duct canalize.
The lecture specifically asks: "What are important differential diagnoses?" [1]
| Condition | Key Distinguishing Features |
|---|---|
| CNLDO (most common) | Epiphora + mucoid discharge + crusting since birth, non-tender, normal eye, resolves by 12m |
| Congenital glaucoma | Epiphora + photophobia + blepharospasm + enlarged eye (buphthalmos) + hazy/enlarged cornea (Haab striae) — THIS IS THE CRITICAL DDx NOT TO MISS |
| Dacryocystitis | Tender swelling over lacrimal sac, may have purulent discharge |
| Conjunctivitis (neonatal) | Red eye, discharge (purulent in gonococcal, watery in chlamydial/viral), consider ophthalmia neonatorum in first month |
High Yield: Don't Miss Congenital Glaucoma!
A tearing infant is usually CNLDO — but always check for buphthalmos (enlarged eye), corneal haziness/enlargement, and photophobia. Congenital glaucoma is sight-threatening and requires urgent surgical treatment (goniotomy or trabeculotomy). Missing it on an exam is a common trap.
| Step | Details |
|---|---|
| Conservative (first 12 months) | Crigler massage (firm downward pressure over lacrimal sac → increases hydrostatic pressure → helps open the membrane at the valve of Hasner) + lid hygiene |
| If not resolved by 12 months | Probing and irrigation under GA — a probe is passed through the NLD to physically open the obstruction. ~90% success rate on first attempt |
| If probing fails | Silicone intubation, balloon catheter dilatation, or dacryocystorhinostomy (DCR) in refractory cases |
Scenario 5: Parents concerned about their 11-month-old boy's eyes. Smartphone photo shown. Ocular alignment is normal on examination. [1]
This is pseudostrabismus — the appearance of strabismus when no true deviation exists.
Why it happens: Many Asian infants have a flat nasal bridge and prominent epicanthal folds that cover the nasal sclera, making the eyes appear convergent ("pseudo-esotropia"). As the face grows and the bridge becomes more prominent, the appearance resolves.
How to confirm: The Hirschberg test shows symmetric corneal light reflexes, and the cover test shows no movement → no true strabismus. The key message: always perform the Hirschberg and cover test rather than relying on appearance alone.
Clinical Pearl
Parents commonly bring photos showing "crossed eyes." If the photo was taken with a smartphone flash slightly off-center, the corneal reflexes may appear asymmetric. Always examine the child yourself with proper testing. Reassure parents after a normal examination.
8. Leukocoria ("White Pupil") (Scenario 6)
Left eye leukocoria — instead of the normal red reflex, a white reflex is seen. [1]
This is the most dangerous topic in the lecture. Leukocoria means something is blocking or replacing the normal clear pathway between the cornea and the retina (which normally produces the red reflex on ophthalmoscopy or flash photography).
Differential diagnoses: [1]
| Cause | Key Features |
|---|---|
| Congenital cataract | Lens opacity; may be bilateral; associated with TORCH infections, Down syndrome, galactosemia, etc. |
| Retinoblastoma (RB) | Most important not to miss; intraocular malignancy; presents 0–3 years; may be bilateral (heritable form) |
| Retinopathy of prematurity (ROP) | Premature infant; abnormal retinal vascularization |
| Persistent hyperplastic primary vitreous (PHPV) | Now called "persistent fetal vasculature"; usually unilateral; microphthalmic eye |
| Coat's disease | Exudative retinal vasculopathy; usually unilateral in boys |
| Vitreous hemorrhage | Blood in vitreous; consider non-accidental injury in young children |
| Uveitis | Inflammatory cells/debris in vitreous; think JIA-associated in children |
| Retinal detachment | Detached retina visible behind lens |
| Choroidal coloboma | Failure of fetal fissure closure; segmental absence of choroid/retina |
| Toxocariasis | Granuloma from Toxocara larva; mimics retinoblastoma |
Severe corneal pathologies that obscure any view of the iris and pupil, by definition, cannot give rise to leukocoria. [1]
Why This Caveat Matters
Leukocoria specifically means a white reflex seen through a visible pupil. If the cornea is so opaque that you can't see the pupil at all, you wouldn't call it leukocoria — you'd call it a corneal opacity. This is a definitional precision that examiners may test.
Why it's the #1 concern: Retinoblastoma is the most common primary intraocular malignancy in children. It carries a ~95% survival rate if detected early but can be fatal if metastatic. Early diagnosis saves both life and vision.
| Feature | Details |
|---|---|
| Genetics | ~40% heritable (germline RB1 mutation, autosomal dominant with high penetrance); ~60% sporadic (somatic RB1 mutation). Heritable form: often bilateral, younger age at diagnosis |
| RB1 gene | Tumour suppressor on chromosome 13q14; "two-hit hypothesis" (Knudson) — both alleles must be inactivated |
| Presentation | Leukocoria (most common presenting sign), strabismus, red eye, orbital cellulitis (advanced), proptosis (extraocular extension) |
| Investigation | Fundoscopy under GA (examination under anaesthesia — EUA), ocular ultrasound, MRI orbits and brain (never biopsy — risk of seeding) |
| Management | Enucleation (advanced unilateral), chemotherapy (systemic or intra-arterial), focal therapy (laser, cryotherapy), external beam radiation (last resort due to second malignancy risk in heritable cases) |
| Screening | Children with family history: regular fundoscopy under GA from birth |
High Yield: Leukocoria DDx
If an exam question shows a child with a white pupil, your answer should be structured: Retinoblastoma must always be considered first. List the full differential (congenital cataract, PHPV, ROP, Coat's disease, etc.), but emphasize that retinoblastoma is the one that will kill the child if missed.
| Feature | Details |
|---|---|
| Causes | Idiopathic (most common), TORCH infections (rubella classically), genetic/syndromic (Down, galactosemia, Lowe syndrome), metabolic |
| Presentation | Leukocoria, poor visual behaviour, nystagmus (if bilateral and dense) |
| Why urgent | Dense cataract in infancy causes severe deprivation amblyopia — the most severe and least reversible form |
| Management | Early surgery (ideally by 6–10 weeks for unilateral dense cataract) + IOL implantation or contact lens correction + aggressive amblyopia treatment |
From congenital rubella syndrome [4]: Permanent manifestations include congenital cataracts, pigmented retinopathy, congenital glaucoma, microphthalmos — all testable ophthalmological findings.
2024 Fourth Summative MCQ Q91: An 8-year-old boy with VA 20/200 both eyes; VA improves to 20/25 through a pinhole. "What is the purpose of a pinhole test?" Answer: To minimise the impact of refractive error on visual acuity. [5]
From first principles: A pinhole limits the light rays entering the eye to a narrow, central beam. This eliminates peripheral rays that would be mis-focused by an incorrect refractive state. Therefore:
- If VA improves with pinhole → the problem is refractive (correctable with lenses).
- If VA does NOT improve with pinhole → the problem is non-refractive (retinal, optic nerve, or cortical pathology).
The pinhole does NOT help with cataracts (in fact, it can slightly worsen vision by reducing overall light), and it does NOT help with macular or optic nerve disease.
DH arranges for all children aged 4–5 years to undergo vision screening at MCHCs. [1]
This is part of the Integrated Child Health and Development Programme (ICHDP) [3]. The screening checks:
- Visual acuity (typically with picture/letter matching tests)
- Ocular alignment (cover test, Hirschberg)
- Red reflex
Why age 4–5? This is:
- Old enough for reliable VA testing with matching tests.
- Young enough that amblyopia treatment (if detected) will still be effective.
- Before the child starts primary school (where poor vision affects learning).
Exam Intelligence
| Trap | Correct Understanding |
|---|---|
| Confusing BCVA with uncorrected VA | Amblyopia = decreased BCVA (even with optimal glasses). Poor uncorrected VA alone may just be refractive error |
| Confusing cover test and uncover test | Cover test → watch the other eye (detects heterotropia). Uncover test → watch the same eye (detects heterophoria) |
| Thinking pinhole helps with cataracts | Pinhole helps with refractive error only. It can worsen vision in cataracts (reduces light entering) |
| Assuming all children with esotropia need surgery | Fully accommodative esotropia corrects with glasses alone. Surgery only for partially/non-accommodative types |
| Missing congenital glaucoma in a tearing infant | Always look for buphthalmos, corneal haze, photophobia. CNLDO is common but congenital glaucoma is the dangerous DDx |
| Thinking pseudostrabismus needs treatment | Normal Hirschberg + cover test → reassure. No treatment needed. Appearance resolves with facial growth |
| Forgetting that grating acuity overestimates VA | A common MCQ distractor: grating (preferential looking) tests overestimate compared to recognition (Snellen) testing |
| If the question says... | Think... |
|---|---|
| Child with poor BCVA, normal eye exam | Amblyopia (refractive if anisometropic, strabismic if squint) |
| White pupil in a child | Leukocoria → DDx list → retinoblastoma first |
| Tearing since birth | CNLDO vs congenital glaucoma (check for big eye, corneal haze) |
| Child with esotropia that corrects with glasses | Fully accommodative esotropia |
| Infant appears cross-eyed but alignment tests normal | Pseudostrabismus (epicanthal folds, flat nasal bridge) |
| VA improves with pinhole | Refractive error |
Past Paper Questions
Stem: An 8-year-old boy attends your clinic for blurring of vision, especially for distant vision. The patient's visual acuity is 20/200 in both eyes. However, he sees more clearly, with visual acuity of 20/25 in both eyes, while looking through a pinhole. What is the purpose of a pinhole test when measuring visual acuity?
Options: A. To maximise the impact of cataracts on visual acuity B. To maximise the impact of refractive error on visual acuity C. To minimise the impact of cataracts on visual acuity D. To minimise the impact of refractive error on visual acuity ✓
Rationale: The pinhole removes peripheral (unfocused) rays, isolating a narrow central beam that is less affected by refractive error. VA improvement with pinhole confirms a refractive cause. Option C is a trap — pinhole reduces overall illumination and doesn't help cataracts.
Stem: A 54-year-old lady with SLE on hydroxychloroquine for 8 years complains of bilateral progressive blurring of vision over 9 months. Most likely cause?
Answer: C. Bull's eye maculopathy ✓
Rationale: Hydroxychloroquine toxicity → retinal toxicity → bull's eye maculopathy. Not directly paediatric ophthalmology, but tested alongside ophthalmology content. Distinguish from: anterior uveitis (SLE association, but would present with pain/redness), CRVO (unilateral, sudden), and AACG (acute painful red eye).
Stem: 69-year-old gentleman with left ptosis, diplopia, impaired left eye adduction/upward/downward gaze, right-sided weakness. (a) Cranial nerves for extraocular movements? (b) Which CN is abnormal? (c) Motor neuron lesion type? (d) Site of lesion? (e) Most likely diagnosis?
Answers: (a) CN III (oculomotor), CN IV (trochlear), CN VI (abducens) (b) CN III (left oculomotor nerve) (c) Upper motor neuron lesion (contralateral weakness + hyperreflexia) (d) Left midbrain (ipsilateral CN III + contralateral UMN signs = Weber syndrome) (e) Left midbrain stroke (Weber syndrome)
Connection to this lecture: Understanding extraocular muscle innervation and strabismus classification helps approach CN palsy questions. Incomitant strabismus in adults = think cranial nerve palsy; in children = think congenital/accommodative causes first.
Integration with Related Material
The strabismus section links directly to GC 124 content on CN III/IV/VI palsies. In children, cranial nerve palsies present as incomitant strabismus (angle changes with direction of gaze). In adults, the same palsies present with diplopia (because the adult brain cannot suppress one image).
Cataracts and retinopathy from rubella are important for the leukocoria differential and for prenatal counselling lectures. CRS ocular features: congenital cataracts, pigmented retinopathy, congenital glaucoma, microphthalmos.
Pre-school vision screening at MCHCs fits into the ICHDP framework. Know that vision screening is one of several surveillance components alongside growth monitoring, developmental surveillance, and hearing screening.
High Yield Summary
Five core problems: Refractive error, amblyopia, strabismus, epiphora, leukocoria.
Visual system is immature at birth — the critical period (~0–9 years) is when intervention works. After this, amblyopia becomes irreversible.
Amblyopia = poor BCVA without structural cause. Types: refractive (most common), strabismic, deprivation. Treatment: correct cause → glasses → patch the good eye.
Strabismus: Use Hirschberg + cover/uncover test. Fully accommodative esotropia corrects with hyperopic glasses alone. Children suppress rather than see double → amblyopia risk.
Epiphora in infants: Usually CNLDO (resolves by 12 months with massage). ALWAYS rule out congenital glaucoma (buphthalmos, Haab striae, photophobia).
Leukocoria: Differential includes retinoblastoma (life-threatening, never biopsy), congenital cataract, ROP, PHPV, Coat's, toxocariasis. Urgent referral.
Pinhole test: Improves VA if refractive error present. Does NOT help with cataracts or retinal disease.
HK DH Pre-School Vision Screening at age 4–5 at MCHCs — know this exists and why this age was chosen.
Myopia control: Low-dose atropine drops (0.01%/0.05%), Ortho-K, DIMS/HALT lenses — all work by reducing peripheral defocus or scleral remodeling signals.
Active Recall - Eye Problems in Children
[1] Lecture slides: GC 123. Eye problems in children.pdf (all pages referenced throughout) [2] Senior notes: Ryan Ho Opthalmology.pdf (pp. 108–109, atropinized refraction and paediatric ophthalmology examination) [3] Senior notes: Adrian Lui Pediatrics Notes.pdf (p. 17, ICHDP and MCHC vision screening) [4] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p. 1829, Congenital Rubella Syndrome) [5] Past papers: 2024 Fourth Summative MCQ.pdf (Q91, pinhole test) [6] Past papers: 2021 Fourth Summative Assessment MCQ.pdf (Q13, hydroxychloroquine maculopathy) [7] Past papers: 2021 Fourth Summative SAQ.pdf (Q6, CN III palsy and Weber syndrome)
GC122 Chronic Visual Loss
Chronic visual loss is a gradual, progressive decline in visual acuity or visual field occurring over weeks to months, commonly caused by conditions such as cataracts, glaucoma, age-related macular degeneration, or diabetic retinopathy.
GC124 Neuro Ophthalmology
Neuro-ophthalmology is the subspecialty concerned with visual disturbances arising from disorders of the central and peripheral nervous system, including optic nerve diseases, cranial nerve palsies, pupillary abnormalities, and disorders of ocular motility.