Acute Onset Painless Vision Loss

Classification: Monocular vs. Binocular

Causes and Differential Diagnosis

1. Central Retinal Artery Occlusion (CRAO)

• Non-arteritic permanent (>2/3 of cases) - equivalent to ischemic stroke of the retina
• Non-arteritic transient - related to vasospasm; may present as TIA of the retina
• Arteritic - due to giant cell arteritis (GCA/temporal arteritis)

• Sudden, profound, painless monocular vision loss (pain suggests GCA)
• VA severely reduced; absence of light perception suggests GCA or ophthalmic artery occlusion
• Relative afferent pupillary defect (RAPD) - profound, sometimes total (amaurotic pupil)
• Fundoscopy: pale/gray-white edematous retina with cherry-red spot at the fovea, attenuated arteries, "cattle-trucking" or "box-car" segmentation of blood column

Acute CRAO: Note the cherry-red spot at the macula with surrounding pale retinal edema (Kanski's Clinical Ophthalmology, 10e)

CRAO with whitening of the retina and less prominent cherry-red spot (Rosen's Emergency Medicine)

2. Branch Retinal Artery Occlusion (BRAO)

• Sudden, profound, painless altitudinal or sectoral visual field loss
• BRAO may go unnoticed if central vision is spared
• RAPD often present
• Fundus: cloudy white "ground glass" retinal edema in affected sector; occluding emboli visible at bifurcation points; "cattle-trucking" of blood column
• FA shows delayed arterial filling and hypofluorescence
• Carries a somewhat better prognosis than CRAO
• Superotemporal quadrant most commonly affected

3. Central Retinal Vein Occlusion (CRVO)

• Non-ischemic CRVO: dilated retinal vessels and edema only; VA >20/200 in over 80% of patients
• Ischemic CRVO: sudden onset of painless monocular vision loss; VA <20/200 in over 90%; major complications are neovascular glaucoma and macular edema

• Dilated and tortuous retinal veins in ALL quadrants
• Flame-shaped hemorrhages throughout all 4 quadrants
• Disc edema and cotton-wool spots

CRVO: "Blood and thunder" appearance with diffuse hemorrhages in all four quadrants (Rosen's Emergency Medicine)

4. Branch Retinal Vein Occlusion (BRVO)

• Blurred vision and metamorphopsia if macula involved; asymptomatic if peripheral
• Flame-shaped and dot/blot hemorrhages confined to the sector drained by the thrombosed vein
• Superotemporal quadrant most commonly affected (at an arteriovenous crossing point)
• Chronic macular edema is the most common cause of persistent poor VA
• Retinal neovascularization occurs in ~8% by 3 years; risk higher with >5 disc areas of non-perfusion on FA

5. Ischemic Optic Neuropathy (ION)

Anterior Ischemic Optic Neuropathy (AION)

• Patients >50 years with systemic vascular disease, diabetes, hypertension
• Precipitated by: anemia, hypovolemia, dehydration, systemic hypotension, nocturnal BP fluctuations, dialysis
• Visual field defect often respects the horizontal midline (altitudinal defect)
• Pale, swollen optic disc; large RAPD

• Extremely rare under 50 years; incidence rises with each decade
• Systemic symptoms: weight loss, malaise, jaw claudication, headache, scalp tenderness, polymyalgia rheumatica, low-grade fever
• In up to 25%, acute vision loss is the ONLY symptom
• Vision loss: unilateral 46%, sequential 37%, simultaneously bilateral 17%
• May be preceded by amaurosis fugax
• Untreated: may progress to involve the other eye
• ESR and CRP are elevated; temporal artery biopsy confirms diagnosis

Posterior Ischemic Optic Neuropathy (PION)

6. Amaurosis Fugax (Transient Monocular Vision Loss)

• Transient, painless monocular vision loss, classically described as "a curtain coming down over the eye"
• Typically lasts minutes, recovery in reverse order of loss
• Usually of embolic origin (from ipsilateral carotid stenosis or cardiac source)
• A TIA equivalent of the retina - warns of impending stroke
• Reported in: 2% of CRAO, 14% of BRAO, 5% of CRVO, 3% of NA-AION, and 32% of GCA with ocular involvement
• Attacks can range from several times daily to once every few months
• Management: same as stroke workup - urgent

7. Vitreous Hemorrhage

• Sudden painless vision loss, often described as "floaters," "haze," or complete visual obscuration
• Causes: proliferative diabetic retinopathy, posterior vitreous detachment with retinal tear, subarachnoid hemorrhage (Terson syndrome), sickle cell disease, trauma
• Fundoscopy: red reflex absent or poor; dark blood in vitreous

8. Retinal Detachment

• Painless visual field loss, often preceded by photopsia (flashing lights) and floaters
• "Curtain" or "shadow" spreading across visual field
• Risk factors: myopia, trauma, prior ocular surgery, family history
• Fundoscopy: detached retina appears elevated and billowing

9. Occipital Cortex Infarction (Cortical/Posterior Visual Pathway)

• Binocular visual field loss (homonymous hemianopia) - affects the same field in both eyes
• Caused by posterior cerebral artery infarction
• Associated neurological symptoms common (except in pure occipital strokes)
• Important: basilar artery territory infarction causes sudden complete bilateral blindness

Key Differentiating Features

Diagnostic Approach

• Onset speed (seconds = vascular; minutes = TIA; gradual = other)
• Monocular vs. binocular (critical - have patient cover each eye)
• Duration (transient = amaurosis fugax; persistent = infarction)
• Associated systemic symptoms (jaw pain, scalp tenderness = GCA; neurological Sx = stroke)
• Risk factors: cardiovascular disease, DM, HTN, atrial fibrillation

• Visual acuity (each eye separately)
• Visual fields (confrontation testing)
• RAPD testing (swinging flashlight test)
• Fundoscopy (critical - most diagnoses can be made here)
• Check for carotid bruits

• ESR, CRP - mandatory if GCA suspected (elevated in >90%)
• Temporal artery biopsy - gold standard for GCA
• CT/MRI brain - cortical causes, posterior pathway pathology
• Carotid Doppler ultrasound - stenosis evaluation
• Echocardiography - cardiac embolic source
• FFA (fluorescein angiography) - delineate extent of ischemia
• Hypercoagulable workup - mandatory in patients under 50 years

Management

CRAO - A True Emergency (Stroke of the Retina)

1. Ocular massage - 10-15 seconds of pressure through closed eyelids then sudden release, for 3-5 minutes; aims to dislodge embolus and promote forward flow
2. Anterior chamber paracentesis - 27-gauge needle to withdraw aqueous humor, acutely lowering IOP to increase perfusion gradient
3. IOP-lowering agents - topical timolol, acetazolamide IV, mannitol
4. Carbogen inhalation (95% O2 + 5% CO2) - causes vasodilation of retinal arteries, increases intra-arterial pCO2
5. IV thrombolysis (tPA) - alteplase 0.9 mg/kg (10% as bolus, remainder over 59 min) if < 4.5 hours from onset for non-arteritic CRAO; intra-arterial thrombolysis if < 6 hours
6. Hyperbaric oxygen (HBO) - theoretical direct oxygenation of retina; current evidence limited to retrospective data

None of the above therapies have been conclusively proven to improve visual outcomes in randomized trials. Treatment should be individualized in consultation with an ophthalmologist.

• 30% of CRAO patients have severe carotid disease, coincidental stroke, or extreme hypertension
• 20% have simultaneous MI or critical heart disease
• ~95% need a change in systemic medication; 25% require urgent surgical intervention
• Antiplatelet therapy (aspirin 600 mg loading dose) unless contraindicated
• Oral anticoagulation for atrial fibrillation
• Carotid endarterectomy for symptomatic stenosis >70%
• Urgent referral to stroke clinic - high risk of cerebrovascular event in the days following

CRVO

• Treat underlying systemic causes (hypertension, diabetes, hyperlipidemia)
• Intravitreal anti-VEGF injections - mainstay for macular edema (bevacizumab, ranibizumab, aflibercept)
• Intravitreal corticosteroid implants (dexamethasone)
• Laser photocoagulation for neovascularization
• Monitor for neovascular glaucoma

Arteritic AION (GCA)

• Ophthalmologic emergency - urgent high-dose IV methylprednisolone (500 mg - 1 g/day for 3 days) to prevent fellow eye involvement
• Then oral prednisolone 1 mg/kg/day
• Temporal artery biopsy (should not delay steroid treatment)
• Long-term steroid taper with monitoring of ESR/CRP

NA-AION

• No proven treatment for the acute episode
• Address underlying vascular risk factors
• Aspirin may reduce risk of fellow eye involvement
• Avoid nocturnal hypotension (especially in dialysis patients)

Amaurosis Fugax

• Urgent workup as for TIA/stroke
• Carotid Doppler, echocardiography, cardiac monitoring (Holter)
• Antiplatelet or anticoagulant therapy based on etiology
• Carotid endarterectomy for high-grade ipsilateral stenosis

Ocular Ischemic Syndrome (OIS)

Key Clinical Pearls

1. Acute angle-closure glaucoma - can cause sudden monocular vision loss but pain is universal; a cloudy/steamy lens is visible. Always rule this out if any doubt exists.
2. CRAO is a stroke equivalent - treat with the same urgency as acute ischemic stroke. The risk of subsequent cerebrovascular events is substantial.
3. GCA is bilateral threat - untreated arteritic AION progresses to bilateral blindness. Steroids must be started immediately, before biopsy results.
4. Always ask about monocular vs. binocular - patients commonly cannot distinguish between unilateral visual loss and a contralateral hemianopia. Have them cover each eye.
5. The pain-vision loss combination - pain with sudden vision loss points to acute angle closure glaucoma, optic neuritis (pain on eye movement), or GCA (jaw pain, headache).
6. Hypercoagulable workup - mandatory in all patients under 50 years with any retinal vascular occlusion.

• Kanski's Clinical Ophthalmology: A Systematic Approach, 10e - Chapters on Retinal Vascular Disease, RAO, RVO, AION
• Rosen's Emergency Medicine: Concepts and Clinical Practice, 10e - Chapter 57: Sudden Monocular Vision Loss
• Tintinalli's Emergency Medicine: A Comprehensive Study Guide
• Bradley and Daroff's Neurology in Clinical Practice