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This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Localise: monocular suggests eye/optic nerve; homonymous field loss suggests retrochiasmal brain lesion.
- Acute painless monocular visual loss may be retinal artery occlusion or ischemic optic neuropathy and needs urgent assessment.
- Age >50 with headache, jaw claudication or visual symptoms is giant cell arteritis until proven otherwise.
- Painful visual loss with eye movement in a young adult suggests optic neuritis and possible demyelination.
- Papilloedema means raised intracranial pressure until proven otherwise.
Approach to the Presentation
Ask monocular versus binocular, field pattern, pain, onset, transient obscurations, headache, jaw claudication, diplopia, neurological symptoms and vascular risk. Test acuity, pupils/RAPD, visual fields, colour vision, fundoscopy and ocular movements.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Giant cell arteritis / arteritic AION | must-not-miss | Age >50, new headache, scalp tenderness, jaw claudication, transient or permanent visual loss | ESR/CRP/platelets; temporal artery ultrasound/biopsy; treat immediately |
| Central retinal artery occlusion | must-not-miss | Sudden painless monocular loss, afferent pupillary defect, cherry-red spot | Fundoscopy; stroke workup |
| Occipital stroke | must-not-miss | Homonymous field defect, cortical visual loss, vascular risk, other posterior signs | CT/CTA/MRI stroke pathway |
| Papilloedema/raised ICP | must-not-miss | Transient visual obscurations, headache worse lying/Valsalva, pulsatile tinnitus, diplopia | Fundoscopy; MRI/MRV then LP opening pressure if safe |
| Retinal detachment | must-not-miss | Flashes, floaters, curtain/shadow over vision | Dilated retinal exam/ocular ultrasound |
| Optic neuritis | common | Painful monocular visual loss, pain on eye movement, reduced colour vision, RAPD, young adult | MRI brain/orbits with contrast |
| Migraine aura | common | Positive shimmering scotoma spreading over minutes, resolves <60 min, often binocular field phenomenon | Clinical after excluding TIA/retinal causes |
| Pituitary/chiasmal compression | less common | Bitemporal hemianopia, headache, endocrine symptoms | MRI pituitary/brain |
| Functional visual loss | less common | Inconsistent field testing, normal objective eye exam | Positive inconsistency after organic causes considered |
Red Flags & Key History
Symptoms
Sudden painless monocular visual loss
Age >50 with headache/jaw claudication
Homonymous field loss or other stroke symptoms
Papilloedema symptoms
Pain with eye movement and colour desaturation
Signs
RAPD
Papilloedema
Cherry-red spot or retinal pallor
Bitemporal hemianopia
Reduced colour vision
Approach to Investigation
First-line
Visual acuity, pupils, visual fields, colour visionLocalises lesion and documents severity.
FundoscopyPapilloedema, retinal pallor, haemorrhage or detachment.
ESR/CRP/plateletsImmediate when giant cell arteritis possible.
Second-line
CT/CTA or MRI brainStroke/retro-chiasmal visual loss or neurological signs.
MRI brain/orbitsOptic neuritis, compressive optic neuropathy or pituitary/chiasmal lesion.
Ocular ultrasoundRetinal detachment if fundus view limited.
Specialist
Urgent ophthalmologyMost acute visual loss; CRAO, retinal detachment, GCA or papilloedema.
Neurology/stroke teamOptic neuritis with demyelination concern, homonymous defects, papilloedema or stroke.
Management Principles
MCC Acute Visual Disturbance/Loss objective + CSBPR stroke approach1
Giant cell arteritis
- Start high-dose glucocorticoids immediately when suspected; do not wait for biopsy
- Urgent ophthalmology/rheumatology
2
Retinal artery occlusion / stroke pattern
- Treat as stroke/TIA equivalent: urgent ophthalmology plus stroke workup
- Assess carotids, cardiac rhythm and vascular risk
3
Optic neuritis
- MRI brain/orbits and neurology/ophthalmology
- Consider IV steroids for severe cases or according to specialist guidance; evaluate MS risk
4
Raised ICP/papilloedema
- Urgent imaging before LP
- Treat cause; acetazolamide/weight management for IIH under specialist care
Complications & Pitfalls
- Not checking fields: homonymous field loss is brain until proven otherwise.
- Delaying steroids in GCA: vision may be lost bilaterally.
- Assuming migraine aura in older vascular patients: sudden negative visual loss requires vascular evaluation.
- Missing RAPD: it strongly supports optic nerve/retinal pathology.
MCCQE1 Exam Tips
- 1Monocular = eye/optic nerve; homonymous = brain.
- 2GCA visual symptoms get steroids immediately.
- 3Optic neuritis is painful eye movement plus colour desaturation/RAPD.
- 4Papilloedema requires urgent imaging before LP.
- 5CRAO is a stroke-equivalent presentation.
- 6Migraine aura is positive and spreading, usually over minutes.
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