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Acute Onset Painless Vision Loss - Detailed Guide

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1. Classification Framework

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2. Central Retinal Artery Occlusion (CRAO)

Mechanism

Types

1. Non-arteritic permanent - most common (~2/3 of cases); equivalent to ischemic stroke of the retina
2. Non-arteritic transient - vasospasm-mediated; resembles a retinal TIA
3. Arteritic - due to giant cell arteritis (GCA); the only type where pain may be present (headache/jaw claudication from GCA, not the eye itself)

Risk Factors

• Age 50-70 years
• Vascular risk factors (HTN, DM, hyperlipidemia, smoking)
• Collagen vascular disease / vasculitis
• Cardiac valvular abnormality (embolic source)
• Sickle cell disease
• Increased orbital pressure (acute glaucoma, retrobulbar hemorrhage)
• In <50 years: hypercoagulable states

Clinical Features

• Sudden, profound, painless monocular vision loss
• VA severely reduced (may be no light perception if GCA or ophthalmic artery occlusion)
• RAPD profound - sometimes a complete amaurotic pupil
• Fundoscopy:
  • Pale, grey-white retinal edema in all quadrants
  • Cherry-red spot at fovea - the intact choroidal circulation shines through the thin foveola against the surrounding pale ischemic retina
  • Attenuated arteries with "cattle trucking" / "box-car" segmentation of blood column
  • Emboli visible in ~20% (especially at bifurcation points)
  • If a cilioretinal artery is present, a sector of normal-colored macula is preserved
• Over days-weeks: cloudiness and cherry-red spot disappear; arteries remain attenuated; late signs: optic atrophy, vascular sheathing, inner retinal atrophy

Prognosis

Management (time window <6 hours)

1. Ocular massage - using a three-mirror contact lens (or through closed eyelids by the patient). Positive pressure 10-15 seconds, then release, for 3-5 minutes. Aim: mechanically collapse artery lumen, cause flow changes, dislodge embolus.
2. Anterior chamber paracentesis - 27-gauge needle, withdraw 0.1-0.2 mL of aqueous humor; reduces IOP and may dislodge embolus. Pre-treat with povidone-iodine 5% + topical antibiotic.
3. IV thrombolysis - if <4.5 hours from onset; intra-arterial thrombolysis if <6 hours. No large RCT exists; heterogeneous evidence. Use is tailored to individual circumstances in consultation with ophthalmology.
4. Hypercoagulable workup - mandated in patients <50 years.
5. Cerebrovascular workup - strong association between retinal artery occlusion and subsequent ischemic stroke; expedited workup for cerebrovascular disease is recommended.

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3. Branch Retinal Artery Occlusion (BRAO)

• Symptoms: Sudden, profound painless altitudinal or sectoral visual field loss. Can go unnoticed if central vision is spared.
• RAPD often present.
• Fundus: Cloudy white "ground glass" retinal oedema corresponding to the ischemic area; one or more emboli visible at bifurcation points; "cattle trucking" in affected artery.
• FA: Delayed arterial filling, hypofluorescence of involved segment.
• Management similar to CRAO. Review at 3 months for fundus appearance and visual fields.
• Kanski's Clinical Ophthalmology 10th Edition, p.552

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4. Central Retinal Vein Occlusion (CRVO)

Mechanism

Risk Factors

Types

• Non-ischemic CRVO: Dilatation and edema only; VA >20/200 in >80% of cases.
• Ischemic CRVO: Sudden onset painless vision loss; VA <20/200 in >90%; associated with severe complications.

Clinical Features

• Vision loss ranges from vague blurring to rapid, painless, monocular loss
• Fundoscopy: Dilated tortuous veins, diffuse retinal hemorrhages in all quadrants ("blood-and-thunder fundus"), disc edema
• Contralateral fundus is normal - this distinguishes CRVO from papilledema

Complications

• Neovascular glaucoma (ischemic CRVO)
• Macular edema

Management

• Treat underlying etiology (HTN, DM, etc.)
• Ophthalmology consult for macular edema management
• Anti-VEGF therapy (intravitreal ranibizumab, bevacizumab)
• Intravitreal corticosteroids
• Retinal photocoagulation / cyclocryotherapy
• Low-molecular-weight heparin shows promise
• Tintinalli's Emergency Medicine; Rosen's Emergency Medicine, p.902

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5. Ischemic Optic Neuropathy (ION)

Classification

A-AION (Arteritic - GCA-related)

• Age typically >70 years (extremely rare <50 years)
• Associated symptoms: headache, scalp tenderness, jaw claudication, polymyalgia rheumatica, fever, malaise, weight loss
• Note: In up to 25%, acute vision loss is the only symptom - no classic GCA features
• Vision loss unilateral (46%), sequential (37%), or simultaneously bilateral (17%)
• Vision is severely reduced - hand motion or worse in ~25%
• Optic disc: Chalky-white edematous appearance with disc hemorrhages
• Concurrent cotton-wool spots on fundus are highly suggestive of A-AION
• Fluorescein angiography: Choroidal hypoperfusion (distinguishes from NA-AION)

• Elevated ESR (typically 70-110 mm/h in biopsy-proven cases)
• Elevated CRP (combination increases diagnostic sensitivity)
• CT angiography: 71% sensitive, 85.7% specific
• MRI: 94% sensitive, 78% specific
• Temporal artery biopsy confirms diagnosis (giant cells + endovascular inflammation)

• Do not wait for biopsy before starting steroids - biopsy remains valid up to 1 week after steroid initiation
• IV methylprednisolone 500 mg - 1 g daily x 3 days (admit for IV)
• Then transition to oral prednisolone
• IV steroids: 34% chance of visual improvement; reduces fellow eye involvement
• Prognosis for visual recovery in the affected eye is poor despite treatment
• Tocilizumab for steroid-resistant or steroid-intolerant patients

NA-AION (Non-arteritic)

• Most common cause of unilateral optic nerve edema in adults >50 years
• Classic risk factors: DM, HTN, obstructive sleep apnea, nocturnal hypotension
• Structural risk factor: congenitally crowded optic nerve head ("disc at risk") - small cup-to-disc ratio; swelling within scleral canal causes compartment syndrome → further ischemia
• Visual field: Altitudinal defects (respecting the horizontal midline)
• Disc: Pale, swollen with nerve fiber hemorrhages
• Moderate visual loss (less severe than A-AION)
• Spontaneous improvement in ~1/3 of patients
• No proven treatment - steroids (systemic + intravitreal) and anti-VEGF tried without success

• Bradley and Daroff's Neurology in Clinical Practice; Rosen's Emergency Medicine, p.902

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6. Retinal Detachment

• Symptoms: Flashing lights (photopsia) and floaters preceding the vision loss; then a dark veil or curtain progressing across the visual field; decreased peripheral then central acuity
• Monocular (binocular flashes/floaters = ophthalmic migraine)
• Fundoscopy (dilated): Large detachment appears as a pale, billowing "parachute" - most tears are peripheral and not visible on direct fundoscopy
• Requires dilated indirect ophthalmoscopy by ophthalmologist within 24 hours
• Ocular ultrasound can confirm in the ED; must be verified by the ophthalmologist
• Tintinalli's Emergency Medicine

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7. Amaurosis Fugax (Transient Monocular Vision Loss)

• Transient monocular vision loss (minutes, resolves completely) - the "TIA of the retina"
• Caused by embolic or vasospastic episode in the ophthalmic/retinal circulation
• Carries significant risk of subsequent permanent vision loss or ischemic stroke
• Reported in: 2% of CRAO, 14% of BRAO, 5% of CRVO, 3% in NA-AION, 32% in GCA with ocular involvement
• Requires urgent vascular workup (carotid imaging, echo, ECG, lipids, coagulation screen)

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8. Cortical/Occipital Causes (Binocular)

• Posterior circulation stroke (basilar artery territory) → sudden bilateral total blindness
• Occipital lobe infarct → sudden homonymous hemianopia (patient may report it as monocular loss on one side)
• Key differentiator: bilateral visual loss with a pupillary reflex intact (cortical blindness preserves pupil reflex as the afferent arc is intact through the midbrain, not the cortex)

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9. Diagnostic Approach

History

• Monocular vs. binocular? - critical first question
• Onset, duration, progression
• Associated symptoms: pain, headache, jaw claudication, floaters, flashes, preceding TIA episodes
• Vascular risk factors, GCA symptoms

Examination

Investigations

• Urgent: Fundoscopy (dilated), visual acuity, visual fields, pupil responses
• Bloods: ESR, CRP (if GCA suspected); FBC, glucose, lipid profile
• If <50 years: Hypercoagulable screen (protein C, S, antithrombin III, antiphospholipid antibodies, Factor V Leiden, homocysteine)
• Imaging: CT/MRI brain (if cortical cause or uncertain diagnosis); carotid Doppler/CTA for embolic source
• Cardiac workup: Echo, ECG (embolic source)
• Temporal artery biopsy if GCA suspected

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10. Disposition Summary

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Key Differentiating Points (High-Yield Summary)

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• Rosen's Emergency Medicine, Concepts and Clinical Practice, Chapter 57 (p. 900-903)
• Kanski's Clinical Ophthalmology, 10th Edition, Chapter 13 (pp. 552-554)
• Tintinalli's Emergency Medicine, Chapter 241 (pp. 1596-1598)
• Bradley and Daroff's Neurology in Clinical Practice, Chapter 16 (p. 260)
• Recent review: Bénard-Séguin et al., Handbook of Clinical Neurology 2026 - Acute retinal artery occlusions (PMID 42217977)