eMedicine Specialties > Ophthalmology > Retina

Central Retinal Artery Occlusion

Author: Robert H Graham, MD, Senior Associate Consultant, Department of Ophthalmology, Mayo Clinic, Scottsdale, Arizona
Coauthor(s): Shehab A Ebrahim, MD, Assistant Professor, Department of Ophthalmology, Tulane University; Vitreoretinal Surgeon, The Retina Institute, LLC
Contributor Information and Disclosures

Updated: Feb 12, 2009

Introduction

Background

In 1859, Van Graefe first described central retinal artery occlusion (CRAO) as an embolic event to the central retinal artery in a patient with endocarditis. In 1868, Mauthner suggested that spasmodic contractions could lead to retinal artery occlusion. There is a multitude of causes of CRAO, but patients typically present with sudden, severe, and painless loss of vision.

Pathophysiology

Visual loss from CRAO occurs from the loss of blood supply to the inner layer of the retina. The ophthalmic artery is the first branch of the internal carotid artery and enters the orbit underneath the optic nerve through the optic canal. The central retinal artery is the first intraorbital branch of the ophthalmic artery, which enters the optic nerve 8-15 mm behind the globe to supply the retina. Short posterior ciliary arteries branch distally from the ophthalmic artery and supply the choroid. Anatomical variants include cilioretinal branches from the short posterior ciliary artery, which gives additional supply to the macula from the choroidal circulation. A cilioretinal artery occurs in approximately 14% of the population.

Acutely, obstruction of the central retinal artery results in inner layer edema and pyknosis of the ganglion cell nuclei. Ischemic necrosis results, and the retina becomes opacified and yellow-white in appearance. The opacity is most dense in the posterior pole as a result of the increased thickness of the nerve fiber layer and ganglion cells in this region. Furthermore, the foveola assumes a cherry-red spot because of a combination of 2 factors: (1) the intact retinal pigment epithelium and choroid underlying the fovea, and (2) the foveolar retina is nourished by the choriocapillaris. The late stage shows a homogenous scar replacing the inner layer of the retina.

Approximately 14% of the general population has cilioretinal arteries and 25% of eyes with acute CRAO have cilioretinal artery. The cilioretinal artery supplies part or all of papillomacular bundle. In 10% of eyes, the cilioretinal artery supplies some or all of the foveola. In such an eye, the visual acuity generally returns to 20/50 or better in 80% of eyes over a 2-week period.

The opacification takes as little as 15 minutes to several hours before becoming evident and resolves in 4-6 weeks. The resulting anatomy reflects a catastrophic insult to the inner retinal layers with attenuated retinal arterioles and optic nerve pallor. Pigmentary changes are typically absent since the retinal pigment epithelium remains unaffected. Boxcar appearance of the blood column can be seen in both arteries and veins. Hayreh has shown that irreversible cell injury occurs after 90-100 minutes of total CRAO in the primate model.¹ Controversy exists regarding the optimal window of treatment in humans, but the conservative approach involves treatment up to 24 hours.

Frequency

United States

CRAO is found in 1 per 10,000 outpatient visits. Of these patients, 1-2% present with bilateral involvement.

Mortality/Morbidity

Patients with visualized retinal artery emboli, whether or not obstruction is present, have a 56% mortality rate over 9 years, compared to 27% for an age-matched population without retinal artery emboli. Life expectancy of patients with CRAO is 5.5 years compared to 15.4 years for an age-matched population without CRAO.

Sex

Men are affected slightly more frequently than women.

Age

The mean age of presentation is in the early 60s, although a few cases have been reported in patients younger than 30 years. The etiology of occlusion changes depending on the age of presentation.

Clinical

History

• The most common presenting complaint is an acute, persistent, painless loss of vision in the range of counting fingers to light perception in 90% of patients. Consider ophthalmic artery occlusion if visual acuity is worse.
• Some patients may reveal a history of amaurosis fugax involving transient loss of vision lasting seconds to minutes but which may last up to 2 hours. The vision usually returns to baseline after an episode of amaurosis fugax.
• Ask about symptoms of temporal arteritis in the older population. Patients complain of sudden, painless, nonprogressive vision loss in one eye. History of headaches, jaw claudication, scalp tenderness, proximal muscle and joint aches, anorexia, weight loss, or fever may be elicited.
• Ask about any medical problems that could predispose to embolus formation (eg, atrial fibrillation, endocarditis, coagulopathies, atherosclerotic disease, hypercoagulable state).
• Prolonged direct pressure to the globe during drug-induced stupor or improper positioning during surgery may lead to CRAO.
• Ask about drug history.

Physical

• Determine the degree of vision loss (eg, no light perception, hand movement, counting fingers).
• Ocular examination includes the following:
  • Check for afferent pupillary defect.
  • Perform an optic nerve examination to look for signs of temporal arteritis. Critical signs include afferent pupillary defect and pale/swollen optic nerve with splinter hemorrhages.
  • Cherry-red spot and a ground-glass retina may take hours to develop.
  • The funduscopic findings typically resolve within days to weeks of the acute event, sometimes leaving a pale optic disc as the only physical finding.
  • Emboli can be seen in about 20% of patients with CRAO.
  • Boxcar segmentation can be seen in both arteries and veins. This is a sign of severe obstruction.
  • Perform a cardiovascular examination for murmurs or carotid bruits.
  • Perform a systemic examination for temporal tenderness, jaw claudication, muscle weakness, and fever to evaluate for temporal arteritis.

Causes

Causes of CRAO vary depending on the age of the patient. A detailed analysis of comorbid disease is necessary to elucidate the cause of the acute visual loss.

• Systemic hypertension seen in two thirds of patients
• Diabetes mellitus
• Cardiac valvular disease seen in one fourth of patients
• Cardiac anomalies, such as patent foramen ovale
• Embolism
  • This is most commonly cholesterol but can be calcific, bacterial, or talc from intravenous drug abuse.
  • This is associated with poorer visual acuity and higher morbidity and mortality.
  • Emboli from the heart are the most common cause of CRAO in patients younger than 40 years.
  • Amaurosis fugax preceding persistent loss of vision suggests branch retinal artery occlusion (BRAO) or temporal arteritis and may represent emboli causing temporary occlusion of the retinal artery.
  • Coagulopathies from sickle cell anemia or antiphospholipid antibodies are more common etiologies for CRAO in patients younger than 30 years.
• Atherosclerotic changes
  • Carotid atherosclerosis is seen in 45% of cases of CRAO, with 60% or greater stenosis in 20% of cases.
  • Atherosclerotic disease is the leading cause of CRAO in patients aged 40-60 years.
• Giant cell arteritis
  • Giant cell arteritis should be considered in patients older than 65 years, but do not ignore in younger patients.
  • Giant cell arteritis may produce CRAO or ischemic optic neuropathy.
  • Giant cell arteritis needs to be treated to preserve vision in the fellow eye.
• Hypercoagulable state
• Collagen vascular disease
• Oral contraceptives
• Polycythemia
• Polyarteritis nodosa
• Rare causes
• Consider in younger patients
• Behçet disease
• Syphilis
• Sickle cell disease
• Migraine
• Increased intraocular pressure from glaucoma or prolonged direct pressure to the globe in unconscious patients
• Hydrostatic arterial occlusion

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