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Central retinal arterial occlusion

Specialties > Ophthalmology

Background knowledge 🧠

Definition

  • Central retinal arterial occlusion (CRAO) is a condition where there is a sudden blockage of the central retinal artery, leading to acute, painless vision loss in one eye.
  • It is considered an ophthalmic emergency requiring immediate medical attention.

Epidemiology

  • Rare condition with an incidence of approximately 1-2 per 100,000 population per year.
  • More common in individuals over 60 years old.
  • Slight male predominance.
  • Higher incidence in patients with cardiovascular risk factors.

Aetiology and Pathophysiology

  • Most commonly caused by an embolism, often from atherosclerotic plaques in the carotid artery or heart.
  • Can also result from thrombosis, particularly in patients with hypercoagulable states.
  • Other causes include vasculitis (e.g., giant cell arteritis), trauma, and rare conditions like sickle cell disease.
  • The occlusion leads to retinal ischemia, causing cell death within minutes.

Types

  • CRAO: Involves the central retinal artery, leading to ischemia of the entire retina.
  • Branch retinal artery occlusion (BRAO): Affects a branch of the central retinal artery, resulting in partial vision loss.
  • Ophthalmic artery occlusion: More severe, affects both the central retinal artery and ciliary circulation.

Clinical Features 🌡️

Symptoms

  • Sudden, painless, monocular vision loss, often described as a curtain descending over the eye.
  • Vision loss is typically severe, with only light perception remaining.
  • No associated redness or eye pain.
  • Some patients may experience a transient visual disturbance (amaurosis fugax) before complete occlusion.

Signs

  • Relative afferent pupillary defect (RAPD) is often present in the affected eye.
  • Fundoscopy reveals a pale retina with a cherry-red spot at the fovea.
  • Segmented (boxcar) appearance of retinal vessels due to sluggish blood flow.
  • Arterial attenuation may be seen.
  • Retinal emboli may be visible.

Investigations 🧪

Tests

  • Urgent fundoscopy to confirm diagnosis.
  • Ocular coherence tomography (OCT) may show retinal thickening.
  • Fluorescein angiography can identify delayed or absent arterial filling.
  • Blood tests: FBC, ESR, CRP (to rule out giant cell arteritis), coagulation profile.
  • Carotid Doppler ultrasound and echocardiography to identify the source of emboli.

Management 🥼

Management

  • Immediate referral to an ophthalmologist.
  • Ocular massage to dislodge embolus, if within 90 minutes of symptom onset.
  • Lower intraocular pressure using IV acetazolamide, topical beta-blockers, or anterior chamber paracentesis.
  • Hyperbaric oxygen therapy may be considered in some cases.
  • Identify and manage underlying cardiovascular risk factors (e.g., antiplatelet therapy for embolic sources).

Complications

  • Permanent vision loss in the affected eye, usually severe.
  • Risk of developing neovascular glaucoma due to retinal ischemia.
  • Increased risk of cerebrovascular events such as stroke.
  • Psychological impact due to sudden visual impairment.

Prognosis

  • Poor visual prognosis, with most patients having significant residual vision loss.
  • Visual recovery is rare and often incomplete, especially if treatment is delayed beyond a few hours.
  • Prognosis worsens with the presence of underlying systemic conditions such as carotid artery disease or atrial fibrillation.

Key Points

  • CRAO is an ophthalmic emergency requiring immediate diagnosis and intervention.
  • Prompt management is critical, but visual outcomes are generally poor.
  • Patients with CRAO should be thoroughly evaluated for cardiovascular risk factors and sources of emboli.
  • Ongoing management of underlying risk factors is essential to prevent further vascular events.

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Ophthalmology