eMedicine Specialties > Emergency Medicine > Ophthalmology

Retinal Artery Occlusion

Author: Neil Jain, MD, Staff Physician, Yale University School of Medicine, Department of Surgery, Section of Emergency Medicine
Coauthor(s): Pascal SC Juang, MD, FAAEM, FACEP, Medical Director, ED Information Systems, Attending Physician, Department of Emergency Medicine, Hoag Memorial Hospital Presbyterian
Contributor Information and Disclosures

Updated: Jun 30, 2009

Introduction

Background

Painless loss of monocular vision is the usual presenting symptom of retinal artery occlusion (RAO). Ocular stroke commonly is caused by embolism of the retinal artery, although emboli may travel to distal branches of the retinal artery, causing loss of only a section of the visual field. Retinal artery occlusion represents an ophthalmologic emergency, and delay in treatment may result in permanent loss of vision.

Immediate intervention improves chances of visual recovery, but, even then, prognosis is poor, with only 21-35% of eyes retaining useful vision. Although restoration of vision is of immediate concern, retinal artery occlusion is a harbinger for other systemic diseases that must be evaluated immediately.

Pathophysiology

Blood supply to the retina originates from the ophthalmic artery, the first intracranial branch of the internal carotid artery that supplies the eye via the central retinal and the ciliary arteries. The central retinal artery supplies the retina as it branches into smaller segments upon leaving the optic disc. The ciliary arteries supply the choroid and the anterior portion of the globe via the rectus muscles (each rectus muscle has 2 ciliary arteries except the lateral rectus, which has 1).

Anatomical variants include cilioretinal branches from the short posterior ciliary artery, giving additional supply to part of the macular retina. A cilioretinal artery occurs in approximately 14% of the population.

Typical funduscopic findings of a pale retina with a cherry red macula (ie, the cherry red spot) result from obstruction of blood flow to the retina from the retinal artery, causing pallor, and continued supply of blood to the choroid from the ciliary artery, resulting in a bright red coloration at the thinnest part of the retina (ie, macula). These findings do not develop until an hour or more after embolism, and they resolve within days of the acute event. By this time, visual loss is permanent and primary optic atrophy has developed. In those with a cilioretinal artery supplying the macula, a cherry red spot is not observed.

Animal studies have shown that a retina with completely occluded circulation has irreversible ischemic damage at 105 minutes but may recover at 97 minutes. Complete occlusion of retinal artery circulation in humans is rare with retinal artery disease; thus, retinal recovery is possible even after days of ischemia.

Branch retinal artery occlusion (BRAO) occurs when the embolus lodges in a more distal branch of the retinal artery. BRAO typically involves the temporal retinal vessels and usually does not require ocular therapeutics unless perifoveolar vessels are threatened. The central retinal artery is affected in 57% of occlusions, the branch retinal artery is involved in 38% of occlusions, and cilioretinal artery obstructions occur in 5% of occlusions.

Frequency

United States

Recent estimates put the incidence of retinal artery occlusion at 0.85 per 100,000 per year, with a 10-year cumulative incidence of 1.5%.

Mortality/Morbidity

• Patients with visualized retinal artery emboli, whether or not obstruction is present, have 56% mortality over 9 years, compared to 27% for an age-matched population without retinal artery emboli. Life expectancy of patients with central RAO (CRAO) is 5.5 years, compared to 15.4 years for an age-matched population without CRAO.
• RAO is associated with smoking and cardiovascular disease, with an increased incidence of stroke in patients who have suffered RAO.
• Both eyes have an equal incidence of disease, with bilateral involvement in 1-2%.

Sex

Men are affected slightly more frequently than women.

Age

• The mean age of presentation of retinal artery occlusion is early in the seventh decade of life, although a few cases have been reported in patients younger than 30 years.
• The etiology of occlusion changes, depending on the age at presentation.

Clinical

History

• The most common presenting complaint is an acute persistent painless loss of vision. In central artery occlusions, visual loss is central and dense. In branch artery occlusions, visual loss may go unnoticed if only a section of the peripheral visual field space is affected.
• A complete visual field defect suggests central retinal artery occlusion (CRAO).
• A sectional visual field defect suggests branch retinal artery occlusion (BRAO) and may be an altitudinal defect affecting the upper or lower hemifield but never respecting a vertical axis.
• A history of hypertension or diabetes mellitus is elicited in 67% and 25% of patients with CRAO, respectively.
• Query about any medical problems that could predispose patients to embolus formation (eg, atrial fibrillation, endocarditis, coagulopathies, atherosclerotic disease).
• Prolonged direct pressure to the globe during drug-induced stupor or improper positioning during surgery also may lead to CRAO.

Physical

• Determine the degree of vision loss (eg, no light perception, hand movement, counting fingers); the prognosis for recovery is directly related to initial visual loss.
• Document hand movement, finger counts, and visual fields at a standard distance of 1' to 3'. Documentation of distance will provide concise communication with consultants and for standardization of repeated examinations.
• Funduscopic examination
  • An afferent pupillary defect (ie, paradoxical dilatation of the pupil when a light is shined from the unaffected eye to the affected eye) may be observed within seconds of the occlusive event.
  • The cherry red spot and a ground-glass retina are the classic findings but 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 observed in approximately 20% of patients with CRAO.
  • A dilated funduscopic examination is required to see the pathological signs of RAO.
  • BRAO presents with whitening of the retina along the distribution of the occluded vessel.
  • Boxcar segmentation of the blood column is observed most often in BRAO and is a sign of severe occlusion and slowing of circulation.
• Direct the physical examination to evaluate for murmurs, carotid bruits, or other signs of cardiovascular disease.

Causes

Causes of central retinal artery occlusion (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.

• Embolism
  • Embolism is usually caused by cholesterol, but it can be calcific, bacterial, or talc from IV drug abuse.
  • It is associated with poorer visual acuity and higher morbidity and mortality than other retinal artery occlusions.
  • Embolus from the heart is 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 common etiologies for CRAO in patients younger than 30 years.
• Atherosclerotic changes
  • Carotid atherosclerosis is observed in 45% of CRAO cases, with 60% or more stenosis occurring in 20% of cases.
  • Atherosclerotic disease is the leading cause of CRAO in patients aged 40-60 years.
• Inflammatory endarteritis
  • Occurrence is rare (only 2% of cases).
  • Suspect inflammatory endarteritis in elderly patients if no other etiology is observed.
  • Inflammatory endarteritis can affect the second eye within hours if untreated.
• Migraines are rare causes of CRAO but are most common in patients younger than 30 years.
• Hydrostatic arterial occlusion
• Moya moya disease
• Thrombophilia
• Carotid dissection
• Increased intraocular pressure (IOP) from glaucoma or prolonged direct pressure to the globe in unconscious patients can precipitate CRAO.
  • Low retinal blood pressure from carotid stenosis or severe hypotension may lead to CRAO.
  • Transection of the retinal artery, transection of the optic nerve, or retrobulbar hemorrhage can cause visual loss.

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