Amaurosis fugax

Amaurosis fugax
The arteries of the choroid and iris. The greater part of the sclera has been removed.
Specialty	Neurology, ophthalmology
Symptoms	Temporary fleeting of vision in one or both eyes
Complications	Stroke[1][2]
Duration	Seconds to hours

Amaurosis fugax (

• Atherosclerotic
  retinal artery or ophthalmic artery, causing a decrease in blood flow to the ipsilateral retina. The most common source of these athero-emboli is an atherosclerotic carotid artery.^[11]
  However, a severely atherosclerotic carotid artery may also cause amaurosis fugax due to its stenosis of blood flow, leading to ischemia when the retina is exposed to bright light.^[12] "Unilateral visual loss in bright light may indicate ipsilateral carotid artery occlusive disease and may reflect the inability of borderline circulation to sustain the increased retinal metabolic activity associated with exposure to bright light."^[13]
• Atherosclerotic ophthalmic artery: Will present similarly to an atherosclerotic internal carotid artery.^{[citation needed]}
• Cardiac
  atrial myxomas.^{[citation needed}
  ]
• Temporary vasospasm leading to decreased blood flow can be a cause of amaurosis fugax.^[14][15] Generally, these episodes are brief, lasting no longer than five minutes,^[16] and have been associated with exercise.^[10][17] These vasospastic episodes are not restricted to young and healthy individuals. "Observations suggest that a systemic hemodynamic challenge provoke[s] the release of vasospastic substance in the retinal vasculature of one eye."^[16]
• Giant cell arteritis: Giant cell arteritis can result in granulomatous inflammation within the central retinal artery and posterior ciliary arteries of eye, resulting in partial or complete occlusion, leading to decreased blood flow manifesting as amaurosis fugax. Commonly, amaurosis fugax caused by giant cell arteritis may be associated with jaw claudication and headache. However, it is also not uncommon for these patients to have no other symptoms.^[18] One comprehensive review found a two to nineteen percent incidence of amaurosis fugax among these patients.^[19]
• Systemic lupus erythematosus^[20][21]
• Periarteritis nodosa^[22]
• Eosinophilic vasculitis^[23]
• Hyperviscosity syndrome^[24]
  • Polycythemia^[25]
• Hypercoagulability^[26]
  • Protein C deficiency^[27]
  • Antiphospholipid antibodies^[28]
    • Anticardiolipin antibodies^[29]
    • Lupus anticoagulant^[30][31]
• Thrombocytosis^[29]
• Subclavian steal syndrome
• Malignant hypertension can cause ischemia of the optic nerve head leading to transient monocular visual loss.^[32]
• Drug abuse-related intravascular emboli[8]
• cardiac bypass.^[29]

• Iritis^[33]
• Keratitis^[24]
• Blepharitis^[24]
• Optic disc drusen^[29]
• Posterior vitreous detachment^[24]
• Closed-angle glaucoma^[34]
• Transient elevation of intraocular pressure^[8][33]
• Intraocular
  hemorrhage^[8]
• Coloboma^[29]
• Myopia^[29]
• Orbital hemangioma^[35]
• Orbital osteoma^[36]
• Keratoconjunctivitis sicca^[29]
  testing

• Optic neuritis^[8]
• Compressive optic neuropathies^[8][29]
• interstitial fluid may all contribute to increases in tissue pressure in the optic nerve head. The consequent reduction in perfusion pressure renders the small, low-pressure vessels that supply the optic nerve head vulnerable to compromise. Brief fluctuations in intracranial or systemic blood pressure may then result in transient loss of function in the eyes."^[37]
  Generally, this transient visual loss is also associated with a headache and optic disk swelling.
• Multiple sclerosis can cause amaurosis fugax due to a unilateral conduction block, which is a result of demyelination and inflammation of the optic nerve, and "...possibly by defects in synaptic transmission and putative circulating blocking factors."^[38]
• Migraine^[39]
• Idiopathic Intracranial Hypertension^[40]
• Intracranial tumor^[40]
• Psychogenic^[24]

Diagnosis

Despite the temporary nature of the vision loss, those experiencing amaurosis fugax are usually advised to consult a

A diagnostic evaluation should begin with the patient's history, followed by a physical exam, with particular importance being paid to the ophthalmic examination with regards to signs of ocular ischemia. When investigating amaurosis fugax, an ophthalmologic consultation is absolutely warranted if available. Several concomitant laboratory tests should also be ordered to investigate some of the more common, systemic causes listed above, including a complete blood count, erythrocyte sedimentation rate, lipid panel, and blood glucose level. If a particular cause is suspected based on the history and physical, additional relevant labs should be ordered.[8]

If laboratory tests are abnormal, a systemic disease process is likely, and, if the ophthalmologic examination is abnormal, ocular disease is likely. However, in the event that both of these routes of investigation yield normal findings or an inadequate explanation, non-invasive duplex ultrasound studies are recommended to identify carotid artery disease. Most episodes of amaurosis fugax are the result of stenosis of the ipsilateral carotid artery.^[41] With that being the case, researchers investigated how best to evaluate these episodes of vision loss, and concluded that for patients ranging from 36 to 74 years old, "...carotid artery duplex scanning should be performed...as this investigation is more likely to provide useful information than an extensive cardiac screening (ECG, Holter 24-hour monitoring, and precordial echocardiography)."^[41] Additionally, concomitant head CT or MRI imaging is also recommended to investigate the presence of a "clinically silent cerebral embolism."^[8]

If the results of the ultrasound and intracranial imaging are normal, "renewed diagnostic efforts may be made," during which fluorescein angiography is an appropriate consideration. However, carotid angiography may not be necessary in the presence of a normal ultrasound and CT.^[42]

Treatment

Fleeting loss of vision does not in itself require any treatment, but it may indicate an underlying condition, sometimes serious, that must be treated. If the diagnostic workup reveals a systemic disease process, directed therapies to treat the underlying cause are required. If the amaurosis fugax is caused by an atherosclerotic lesion, use of aspirin as an anticoagulant is indicated, and a carotid endarterectomy considered based on the location and grade of the stenosis. Generally, if the carotid artery is still patent, the greater the stenosis, the greater the indication for endarterectomy. "Amaurosis fugax appears to be a particularly favorable indication for carotid endarterectomy. Left untreated, this event carries a high risk of stroke; after carotid endarterectomy, which has a low operative risk, there is a very low postoperative stroke rate."^[43] However, the rate of subsequent stroke after amaurosis is significantly less than after a hemispheric TIA, therefore there remains debate as to the precise indications for which a carotid endarterectomy should be performed. If the full diagnostic workup is completely normal, patient observation is recommended.^[8]

See also

• Amaurosis
• Hemianopsia
• Ocular ischemic syndrome
• Retinal migraine

References