Diplopia
Diplopia is the perception of two images of a single object, resulting from misalignment of the visual axes or optical disturbances.
Murtagh Diagnostic Strategy
| Category | Diagnosis | Key Discriminator | Cantonese Question / Finding | Probability |
|---|---|---|---|---|
| Probability Diagnosis | Microvascular CN VI palsy (DM/HTN) | Elderly + vascular RFs + horizontal diplopia + pupil-sparing, self-limiting 6–12 weeks [3][7] | 「你有冇糖尿或者高血壓？」 | ~20% |
| Microvascular CN III palsy (DM/HTN) | Pupil-sparing ptosis + diplopia in elderly with DM/HTN [7] | 「眼皮有冇垂低？個瞳孔正唔正常？」(pupil spared) | ~5% | |
| Serious Not To Miss | Stroke / brainstem lesion | Acute onset + other neurological deficits (hemiparesis, dysarthria) | 「有冇手腳突然無力或者講嘢唔清楚？」 | ~5% |
| NPC (nasopharyngeal carcinoma) | HK-prevalent; CN VI palsy + nasal symptoms + neck mass [8] | 「鼻有冇塞或者流鼻血？頸有冇粒嘢？」 | ~2% | |
| Raised ICP (tumour/hydrocephalus) | Bilateral CN VI (false localising) + headache + papilloedema [3] | 「兩隻眼都有重影？有冇頭痛同嘔？」 | ~1% | |
| PComm aneurysm (surgical CN III palsy) | Painful CN III + pupil-involving (mydriasis) → neurosurgical emergency [3] | 「隻眼有冇痛？瞳孔有冇變大？」 | ~1% | |
| Giant cell arteritis (GCA) | Age > 50 + temporal headache + jaw claudication + ↑ESR | 「太陽穴有冇痛？食嘢嗰陣顎骨會唔會攰痛？」 | < 1% | |
| Pitfalls | Decompensated phoria (latent squint) | Intermittent, worse when tired; no CN palsy signs; corrects with prism | 「係咪時有時冇，攰先出現？」 | ~10% |
| Myasthenia gravis | Fatigable, variable, diurnal; ptosis worsens with sustained upgaze; may mimic any CN palsy [2][4] | 「攰嘅時候重影同埋眼皮垂會唔會嚴重啲？」 | ~5% | |
| Thyroid eye disease (Graves' ophthalmopathy) | Restrictive (not paralytic) EOM limitation; proptosis, lid retraction; most commonly IR > MR [5][6] | 「隻眼有冇凸咗？向上望有冇困難？」 | ~3% | |
| Masquerades | DM neuropathy | Known DM + acute mononeuropathy (CN III or VI); usually pupil-sparing [7] | 「你嘅糖尿控制得點？」 | ~10% |
| Drugs (anticonvulsants, benzodiazepines) | Temporal relationship with medication; bilateral horizontal gaze-evoked nystagmus | 「最近有冇開始食新藥？」 | ~2% | |
| Trying to Tell Me Something? | Health anxiety / fear of stroke or tumour | Excessive worry, functional impairment disproportionate to signs | 「你最擔心係咩嘢？」 | ~10% |
Minute-by-Minute 6-Minute Consultation
| Time | Task | Cantonese Key Phrases | Why It Scores Marks |
|---|---|---|---|
| 0:00–0:30 | Friendly opening, rapport, set agenda | 「你好呀，我係X醫生，今日想傾下你嘅問題，方唔方便你講下有咩嘢唔舒服？」 | Warm greeting, patient-centred opening scores interpersonal marks |
| 0:30–2:00 | HPI – symptom analysis of diplopia | 「你係咩時候開始覺得有重影？」「你閂咗一隻眼仲有冇重影呀？」(binocular vs monocular) 「個重影係左右分開定上下分開？」「係一路咁定係時有時冇？」「望邊個方向最明顯？」 | Binocular vs monocular is the critical first question – monocular = ocular cause, binocular = neurological/muscular [1] |
| 2:00–3:00 | Red flags & associated symptoms | 「有冇頭痛或者嘔？」「隻眼有冇痛？」「有冇面或者手腳麻痺無力？」「講嘢有冇唔清楚？」「眼皮有冇垂低咗？」「有冇瘦咗或者心跳好快？」 | Screens for raised ICP, stroke, aneurysm, GCA, MG, thyroid disease |
| 3:00–3:45 | PMH, DHx, FHx, Social Hx | 「你有冇長期病，例如糖尿、高血壓、甲狀腺嘅問題？」「食緊咩藥？」「有冇對咩藥敏感？」「屋企人有冇類似嘅情況？」「你做咩工作？食唔食煙飲唔飲酒？」 | DM + HTN → microvascular CN palsy; smoking → NPC risk in HK |
| 3:45–4:30 | ICE – uncover hidden agenda | 「你自己覺得隻眼點解會咁？」(Ideas) 「你最擔心嘅係咩嘢？」(Concerns) 「你嚟睇醫生最想我幫你做啲咩？」(Expectations) | ICE marks are heavily weighted; the hidden agenda may be fear of stroke or brain tumour |
| 4:30–5:15 | Functional impact & psychosocial | 「重影有冇影響你返工或者揸車？」「你有冇因為咁覺得好擔心或者瞓唔著？」 | Captures social/psychological problems for biopsychosocial section |
| 5:15–5:45 | Summarise & check understanding | 「等我同你總結一下：你…（重複重點）…我有冇漏咗啲咩？」 | Shows active listening; scores summarising/checking marks |
| 5:45–6:00 | Close with plan & safety net | 「我想幫你安排驗血同埋照下腦，如果突然間頭好痛、手腳無力或者隻眼完全唔郁得，要即刻去急症室。」 | Safe closure with red-flag safety net |
Uncovering the hidden agenda: Ask 「你今日點解決定嚟睇醫生？」— the patient may have tolerated diplopia for days but came today because of a specific fear (e.g., "Am I having a stroke?" or worry about a brain tumour). This is often different from the symptom itself.
| Domain | English Question | Cantonese Question | Why It Matters | If Positive Think Of |
|---|---|---|---|---|
| Monocular vs binocular | Does covering one eye fix the double vision? | 「你閂咗一隻眼，重影有冇消失？」 | Most important first question [1] – monocular = refractive/lens/corneal; binocular = CN palsy/NMJ/orbital | Monocular → cataract, astigmatism; binocular → CN III/IV/VI palsy, MG, TED |
| Onset & duration | When did it start? Sudden or gradual? | 「幾時開始？係突然定慢慢嚟？」 | Sudden → vascular (stroke, aneurysm); gradual → tumour, TED, MG | Sudden + pain → PComm aneurysm emergency |
| Direction of separation | Are the images side by side or on top of each other? | 「兩個影像係左右分開定上下分開？」 | Horizontal → CN VI; vertical → CN IV; mixed → CN III [1] | Horizontal on ipsilateral gaze → CN VI palsy [3] |
| Gaze direction | Which direction makes it worst? | 「望邊個方向重影最嚴重？」 | Identifies affected muscle/nerve | Worst on left gaze → left LR (CN VI) or right MR |
| Diurnal variation | Is it worse towards end of day or when tired? | 「到咗夜晚或者攰嘅時候有冇差啲？」 | Diurnal variation is hallmark of myasthenia gravis [2][4] | Fatigable diplopia + ptosis → MG |
| Ptosis | Does your eyelid droop? | 「眼皮有冇垂低咗？」 | CN III palsy, MG, Horner syndrome | Ptosis + mydriasis → CN III (surgical); ptosis + miosis → Horner |
| Pain | Any eye pain or headache? | 「隻眼或者頭有冇痛？」 | Painful CN III → PComm aneurysm until proven otherwise [3] | Painful → aneurysm, GCA, cavernous sinus thrombosis, migraine |
| Neurological | Weakness, numbness, slurred speech, swallowing difficulty? | 「有冇手腳無力、面麻痺、講嘢唔清楚或者食嘢難吞？」 | Stroke, brainstem lesion, MG (bulbar) | Hemiparesis → stroke; dysphagia + diplopia → MG or brainstem |
| Headache/vomiting | Headache, nausea, vomiting? | 「有冇頭痛、作嘔或者嘔？」 | Raised ICP → CN VI false localising sign [3] | Bilateral CN VI + headache → raised ICP |
| Thyroid symptoms | Weight loss, palpitations, heat intolerance, eye bulging? | 「有冇瘦咗、心跳快、怕熱或者隻眼凸咗？」 | Graves' ophthalmopathy causes diplopia via EOM infiltration [5][6] | Proptosis + lid retraction + diplopia → TED |
| PMH | DM, HTN, hyperlipidaemia, thyroid disease, cancer? | 「有冇糖尿、高血壓、膽固醇高、甲狀腺病或者癌症？」 | DM/HTN → microvascular CN palsy (most common cause in elderly) [3][7] | Microvascular CN palsy usually pupil-sparing, self-limiting 6–12w |
| Drug history | Current medications? | 「而家食緊咩藥？」 | Some drugs cause diplopia (anticonvulsants, sedatives) | Drug-induced diplopia |
| Smoking/alcohol | Do you smoke or drink? | 「你有冇食煙飲酒？」 | Smoking is RF for NPC (common HK malignancy causing CN palsy) [8] and worsens Graves' ophthalmopathy [5] | NPC → CN VI palsy + nasal symptoms |
| Occupation/driving | Do you drive? What is your job? | 「你有冇揸車？做咩工作？」 | Functional impact; safety concern | Driving with diplopia is dangerous |
| Family history | Any family history of thyroid disease, autoimmune disease? | 「屋企人有冇甲狀腺或者免疫系統嘅病？」 | MG, Graves' disease | Autoimmune clustering |
Case Report Form Answer Builder
Template: "Double vision (diplopia) for [duration]. Binocular / monocular. [Horizontal / vertical / oblique] image separation, worst on [direction] gaze. [Sudden / gradual] onset. [Constant / intermittent / diurnal variation]. Associated [ptosis / pain / headache / neurological symptoms / thyroid symptoms] or none. PMH: [DM / HTN / thyroid disease]. No [red flags] / presence of [red flags]."
Key HPI points to capture:
- Binocular vs monocular (the single most important distinction) [1]
- Direction and pattern of image separation
- Onset, duration, progression
- Associated symptoms (pain, ptosis, other CN deficits, systemic)
- Vascular risk factors
- Functional impact
| Likely RFC Examples | How to Phrase |
|---|---|
| Fear of serious cause (stroke, brain tumour) | "Patient is concerned that diplopia may indicate a serious brain condition" |
| Functional impairment (cannot drive/work safely) | "Diplopia interfering with ability to work/drive safely" |
| Referred by optometrist/another doctor | "Referred for further evaluation of new-onset diplopia" |
Best single answer: Choose the reason the patient gives when you ask 「你今日點解決定嚟睇醫生？」— this is often the fear, not just the symptom.
| Component | Likely Content | Exact Wording |
|---|---|---|
| Ideas | "I think I might be having a stroke" / "Maybe my diabetes is affecting my eyes" | Patient thinks the diplopia may be caused by [stroke / diabetes / brain problem] |
| Concerns | Fear of blindness, brain tumour, stroke | Patient is worried about having a [brain tumour / stroke / going blind] |
| Expectations | Wants brain scan, blood tests, specialist referral | Patient expects [brain imaging / blood tests / referral to ophthalmologist or neurologist] |
For a typical FM station with an elderly patient with DM/HTN presenting with acute painless binocular horizontal diplopia, pupil-sparing → Microvascular sixth nerve palsy (ischaemic cranial mononeuropathy)
Minimum supporting evidence:
- Binocular horizontal diplopia worst on ipsilateral gaze
- Pupil-sparing
- Background of DM/HTN
- Painless or mild periorbital ache
- No other neurological deficits
If the stem features diurnal variation + fatigable ptosis → think Myasthenia Gravis [2][4] If the stem features proptosis + lid retraction + thyroid history → think Graves' ophthalmopathy [5][6]
| DDx | One Key Discriminator |
|---|---|
| Posterior communicating artery aneurysm | Painful CN III palsy with pupil involvement (mydriasis) – neurosurgical emergency [3] |
| Myasthenia gravis | Fatigable, variable diplopia + ptosis with diurnal worsening; no pupil involvement [2][4] |
| Thyroid eye disease (Graves' ophthalmopathy) | Restrictive EOM limitation (esp upgaze), proptosis, lid retraction, thyroid history [5][6] |
Alternative DDx depending on stem: NPC (CN VI + nasal Sx + neck mass in HK), brainstem stroke (acute + other neuro deficits), raised ICP (bilateral CN VI + headache + papilloedema)
| Domain | Problem |
|---|---|
| Biological | Underlying poorly controlled DM/HTN causing microvascular cranial neuropathy |
| Psychological | Anxiety and fear of serious intracranial pathology (stroke/tumour) |
| Social/Functional | Unable to drive or work safely due to diplopia; risk of falls |
| Diagnosis/DDx | Best Supporting Physical Sign | How to Elicit It | Why It Supports This Diagnosis |
|---|---|---|---|
| Microvascular CN VI palsy (most likely dx) | Impaired abduction of affected eye with esotropia in primary gaze | Ask patient to follow your finger in H-pattern; observe limitation of lateral movement of affected eye [3] | CN VI innervates lateral rectus; isolated abduction deficit with pupil-sparing in patient with vascular RFs = microvascular CN VI palsy |
| PComm aneurysm (CN III palsy) | Mydriatic fixed pupil + ptosis + "down and out" eye | Inspect pupil size, test pupillary light reflex, observe eye position and movement [3] | Parasympathetic fibres on surface of CN III compressed first by aneurysm → pupil involvement distinguishes surgical from medical CN III palsy |
| Myasthenia gravis | Fatigable ptosis on sustained upgaze (1 minute) | Ask patient to look up at your finger for 60 seconds; observe progressive drooping of eyelid [2][4] | NMJ fatigue → ptosis increases with sustained effort; also Cogan's lid twitch sign |
| Graves' ophthalmopathy | Proptosis with lid retraction and restriction of upgaze | Inspect from above for proptosis; note lid retraction (sclera visible above iris); test upgaze → restricted [5][6] | EOM infiltration (IR most common) restricts upgaze; restrictive pattern (sharp stop) differs from paralytic (weak drift) |
| Raised ICP | Papilloedema on fundoscopy | Fundoscopy: look for blurred disc margins, elevated optic disc, loss of venous pulsation | CN VI is a false localising sign in raised ICP; papilloedema confirms elevated ICP |
| NPC | Posterior cervical / Level II lymphadenopathy + CN VI palsy [8] | Palpate posterior triangle / upper deep cervical LN; inspect with nasopharyngoscopy (specialist) | NPC commonly presents as neck mass in HK; CN involvement from skull base erosion |
Exam Discriminators and Traps
Top Traps That Lose Marks
-
Forgetting to ask binocular vs monocular – This is the single most important question. Monocular diplopia is NOT a CN palsy – it's refractive/lens/corneal. If you don't ask this, you lose the entire diagnostic framework. [1]
-
Missing pupil involvement in CN III palsy – A CN III palsy with mydriasis (pupil-involving) = PComm aneurysm until proven otherwise → urgent referral. Pupil-sparing = likely microvascular. This distinction is life-saving. [3]
-
Forgetting myasthenia gravis – MG can mimic ANY cranial nerve palsy. The clue is fatigability and diurnal variation. Always ask about worsening towards end of day. [2][4]
-
Not asking about NPC in a Hong Kong patient – Nasal symptoms (epistaxis, obstruction, post-nasal drip) + CN palsy + neck mass → NPC. Young patients ( < 55y) with CN VI palsy in HK should have NPC excluded [8]
-
Not asking ICE – Marks are heavily weighted on ICE. The patient often has a specific fear (stroke, tumour). If you don't ask, you lose these marks even if your clinical reasoning is perfect.
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Calling monocular diplopia "CN palsy" – Monocular diplopia persists with one eye covered and is due to refractive error, cataract, or corneal irregularity. Never a neurological emergency.
| Red Flag | Concern | Action |
|---|---|---|
| Painful CN III + pupil involvement | PComm aneurysm → SAH risk | Immediate A&E → urgent CTA/MRA |
| Acute diplopia + hemiparesis/dysarthria | Brainstem stroke | Call 999 |
| Bilateral CN VI + headache + papilloedema | Raised ICP (tumour/hydrocephalus) | Same-day A&E → urgent CT brain |
| Age > 50 + new headache + jaw claudication | GCA → risk of blindness | Urgent ESR/CRP + start steroids |
| Progressive CN palsy + nasal symptoms (HK) | NPC | Urgent ENT referral + nasopharyngoscopy |
「如果突然頭好痛、手腳無力、講嘢唔清楚、或者隻眼瞳孔變大，要即刻去急症室。」
Key GC slide point [1]: A focused clinical history for diplopia should determine: binocular or monocular; persistent or transient (diurnal?); sudden or gradual onset; horizontal, vertical, diagonal, or rotational separation; painless or painful. This is the exam framework for approaching ANY diplopia case.
High Yield Summary
What to ASK:
- Binocular or monocular? (Cover one eye)
- Direction of image separation (horizontal/vertical/oblique)
- Onset (sudden/gradual), diurnal variation
- Pain? Ptosis? Pupil change?
- Neurological symptoms (weakness, speech, swallowing)
- Thyroid symptoms, DM/HTN history
- NPC symptoms (nasal bleeding/obstruction, neck lump) – especially in HK
- ICE: "What are you most worried about?"
What to WRITE:
- Chief complaint: binocular diplopia + onset + direction + associated features + vascular RFs
- Most likely dx: microvascular CN palsy (if elderly + DM/HTN + pupil-sparing) OR MG (if fatigable + diurnal)
- DDx: PComm aneurysm, MG, TED (or NPC/stroke/raised ICP)
- Physical sign: limited EOM in specific direction; check pupil; sustained upgaze test for MG
What NOT to MISS:
- Pupil-involving CN III = aneurysm until proven otherwise → immediate referral
- Bilateral CN VI = raised ICP → urgent imaging
- Young patient with CN VI in HK → rule out NPC
- Fatigable/variable = think MG
Active Recall - Family Medicine Clinical Test
[1] Lecture slides: GC 124. Neuro Ophthalmology.pdf (p24 – Diplopia: focused clinical history framework) [2] Senior notes: Maksim Medicine Notes.pdf (p272 – Myasthenia gravis: ocular features, Cogan's lid twitch, diurnal variation) [3] Senior notes: Ryan Ho Opthalmology.pdf (p82–85 – CN III, IV, VI palsies: clinical features, causes, evaluation) [4] AOS material: AOS - Ophthalmology.pdf (p27 – Scenario 3 Patient 2: MG presentation with fatigable diplopia and ptosis) [5] Senior notes: Ryan Ho Endocrine.pdf (p26–27 – Graves' ophthalmopathy: clinical features, EOM pattern, evaluation) [6] Senior notes: Block A - I am losing weight and sweating all the time (p28, 31, 33 – Graves' ophthalmopathy with diplopia and ophthalmoplegia) [7] Senior notes: Ryan Ho Endocrine.pdf (p97 – Diabetic mononeuropathy: CN III and CN VI palsy, pupil-sparing) [8] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (p251 – NPC: diplopia from CN III/IV/VI compression, nasal symptoms)
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