Acute Vision Loss

Differential Diagnoses

It can be helpful to categorise causes based on anatomical location or pathophysiology (neurological, vascular, ocular).

1. Neurological Causes

   • Cerebellar stroke (posterior circulation): Typically associated with other neurological deficits (e.g. ataxia, dysarthria). May present with visual field defects if the occipital lobe is involved.

   • Retinal migraine: Transient monocular or binocular visual disturbance, often followed by typical migraine headache.

   • Migraine aura: Visual aura can cause flashing lights, scotomas, or transient visual loss.

   • Optic nerve lesions:

     • Optic neuritis: Painful vision loss, common in multiple sclerosis or post-viral.

     • Compressive tumours (e.g. glioma, meningioma): Gradual vision changes, may see optic disc swelling on fundus exam.

     • Papilloedema: Usually bilateral; raised intracranial pressure signs (headache, vomiting).

2. Vascular Causes

   • Arterial:

     • Amaurosis fugax: Transient monocular vision loss (“curtain coming down”), often due to an embolus from the carotid or cardiac source.

     • Giant cell arteritis (GCA): Usually in patients >50 years; often presents with headache, jaw claudication, scalp tenderness, elevated inflammatory markers. Emergency—risk of permanent blindness.

     • Central retinal artery occlusion (CRAO): Sudden, painless, severe monocular vision loss; fundoscopy shows a pale retina with a cherry-red spot at the fovea.

   • Venous:

     • Central retinal vein occlusion (CRVO): Painless vision loss; fundoscopy shows “blood and thunder” appearance (widespread retinal haemorrhages).

3. Ocular Causes

   • Retinal:

     • Retinal detachment: Flashes of light, floaters, and a “curtain” or shadow over vision. This is an ophthalmic emergency.

     • Macular hole: Central vision loss, metamorphopsia (distorted vision).

   • Vitreous:

     • Vitreous haemorrhage: Presents with sudden visual loss, possibly “red haze” or floaters; common in diabetic retinopathy or trauma.

     • Posterior vitreous detachment (PVD): Often causes flashes and floaters; usually benign but can precede retinal detachment.

   • Corneal:

     • Keratitis (e.g. microbial, herpetic), corneal abrasions: Painful, red eye, photophobia, blurred vision.

   • Other:

     • Acute glaucoma (angle-closure crisis): Painful red eye, halos around lights, mid-dilated pupil, elevated intraocular pressure.

     • Uveitis/Iridocyclitis: Pain, photophobia, possible floaters.

Key History Features

1. Flashing lights

   • Suggestive of retinal involvement or posterior vitreous detachment.

2. Floaters

   • Seen in PVD, retinal detachment, or vitreous haemorrhage.

3. Precipitating factors (e.g. coughing, exertion)

   • Can point to embolism or acute mechanical strain that leads to retinal detachment or haemorrhage.

4. Headache/scalp pain

   • Alert for Giant Cell Arteritis.

5. Painful vs. Painless Loss

   • Painful: Optic neuritis, acute glaucoma, uveitis.

   • Painless: CRAO, CRVO, retinal detachment, amaurosis fugax, vitreous haemorrhage.

6. Temporal profile

   • Sudden onset: Vascular occlusion (CRAO, CRVO), retinal detachment, haemorrhage.

   • Progressive: Tumours, papilloedema, corneal opacities.

7. Associated symptoms

   • Jaw claudication (GCA).

   • Neurological deficits (stroke).

   • Floaters/flashes (retinal detachment/PVD).

Investigations

Depending on clinical suspicion, investigations may include:

• Blood tests

  • ESR, CRP: Rule out GCA if patient >50 years or suspicious symptoms.

• Imaging

  • Carotid ultrasound / Echocardiogram: Searching for an embolic source in CRAO or amaurosis fugax.

  • MRI/MRV (brain and orbit): For optic neuritis, compressive lesions, venous sinus thrombosis.

  • CTA/MRA: Assessment of the posterior circulation in suspected stroke or vascular anomalies.

  • CT Orbit: Trauma, suspected tumour or abscess.

  • Lumbar puncture (LP): If raised intracranial pressure or suspected papilloedema (only after imaging to exclude mass lesion).

• Ophthalmology-specific

  • Fundoscopy: Look for retinal detachment (elevated retina), CRAO (pale retina, cherry-red spot), CRVO (blood and thunder), optic disc swelling, or papilloedema.

  • Ocular ultrasound: Helps confirm retinal detachment or vitreous haemorrhage if fundoscopy is difficult.

Management Approaches

1. Retinal Detachment

   • Ophthalmic emergency. Urgent referral to ophthalmology for possible surgical intervention (e.g. pneumatic retinopexy, vitrectomy).

2. Giant Cell Arteritis

   • If strongly suspected, start high-dose corticosteroids immediately (e.g. oral prednisone 1 mg/kg/day) to prevent further vision loss.

   • Arrange urgent temporal artery biopsy (ideally within 1–2 weeks of starting steroids).

3. CRAO (Central Retinal Artery Occlusion)

   • Emergency; immediate ophthalmology referral.

   • Possible acute treatments include ocular massage, lowering intraocular pressure (e.g. IV acetazolamide), hyperbaric oxygen (in some centres).

   • Investigate embolic sources (carotid, cardiac).

4. CRVO (Central Retinal Vein Occlusion)

   • Ophthalmology referral; may benefit from intravitreal anti-VEGF injections.

   • Control risk factors (hypertension, diabetes, hyperlipidaemia).

5. Optic Neuritis

   • Often associated with multiple sclerosis.

   • High-dose IV methylprednisolone can hasten recovery (but does not change final visual outcome).

6. Vitreous Haemorrhage

   • Identify and treat underlying cause (e.g. diabetic retinopathy, trauma, retinal tear).

   • If unresolved, might require surgical intervention (vitrectomy).

7. Acute Glaucoma

   • Immediate referral for reducing intraocular pressure (e.g. IV acetazolamide, topical beta-blockers, pilocarpine).

8. Migraine Aura / Retinal Migraine

   • Usually transient; manage as per migraine protocols if no other cause found.

9. Supportive Measures

   • Pain management if required.

   • Ensure the other eye is protected; address modifiable risk factors (e.g. controlling BP, diabetes, cessation of smoking).

Key Notes

• Posterior Vitreous Detachment (PVD): Common between ages 40–70. Usually benign but must be evaluated to rule out or monitor for retinal detachment.

• Retinal Detachment: Sudden vision loss with floaters and flashes is urgent. “Curtain coming down” or shadow. Prompt surgical intervention is crucial.

• Vitreous Haemorrhage: Often presents with “red-tinted” vision or dark floating spots; treat underlying cause (e.g. diabetic retinopathy).

• GCA: Requires immediate high-dose steroids if suspected, even before confirmation, to prevent bilateral blindness.

• Painful vs. Painless: Distinguish quickly in history for direction of investigations.

• Imaging: Must be performed if neurological or vascular cause is suspected, or if papilloedema is a possibility.