Amaurosis fugax

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Amaurosis (Greek meaning darkening, dark, or obscure) is vision loss or weakness that occurs without an apparent lesion affecting the eye [2]. It may result from either a medical condition or from excess acceleration, as in flight. The term is the same as the Latin gutta serena. Amaurosis fugax (Latin fugax meaning fleeting, Greek amaurosis meaning darkening, dark, or obscure) is a transient monocular visual loss.^[1] Amaurosis fugax (Latin: fugax meaning fugitive) is a temporary loss of vision in one eye caused by decreased blood flow (ischemia) to the retina. Another cause is the presence of emboli located in the ipsilateral(same side) internal carotid artery. It is a type of transient ischaemic attack (TIA). Those experiencing Amaurosis usually experience complete symptom abeyance within a few minutes.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Prior to 1990, amaurosis fugax could, “clinically, be divided into four identifiable symptom complexes, each with its underlying pathoetiology: embolic, hypoperfusion, angiospasm, and unknown.”^[1] In 1990, the causes of amaurosis fugax were better refined by Amaurosis Fugax Study Group, which has defined five distinct causes of transient monocular blindness: embolic, hemodynamic, ocular, neurologic, and idiopathic.^[2] Concerning the pathology underlying these causes (stay idiopathic), “some of the more frequent causes include atheromatous disease of the internal carotid or ophthalmic artery, vasospasm, optic neuropathy, giant cell arteritis, angle-closure glaucoma, increased intracranial pressure, orbital compressive disease, a steal phenomenon, and blood hyperviscosity or hypercoagulability.”^[3]

With respect to embolic and hemodynamic causes, this transient monocular visual loss ultimately occurs due to a temporary reduction in retinal artery, ophthalmic artery, or ciliary artery blood flow, leading to a decrease in retinal circulation which, in turn, causes retinal hypoxia.^[4] Also, it must be noted that while, classically and most commonly, emboli causing amaurosis fugax are described as coming from an atherosclerotic carotid artery, any emboli arising from vasculature preceding the retinal artery, ophthalmic artery, or ciliary arteries may cause this transient monocular blindness.

• Atherosclerotic carotid artery: Amaurosis fugax may present as a type of transient ischemic attack (TIA), during which an embolus unilaterally obstructs the lumen of the retinal artery or ophthalmic artery, causing a decrease in blood flow to the ipsilateral retina. The most common source of these thromboemboli is an atherosclerotic carotid artery.^[5]
  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.^[6] “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.”^[7]

• Atherosclerotic ophthalmic artery: Will present similarly to an atherosclerotic internal carotid artery.

• Cardiac emboli: Emboli arising from the heart may also cause luminal obstruction of the retinal, ophthalmic, and/or ciliary arteries, causing a decrease in blood flow to the ipsilateral retina; examples being those arising due to (1) atrial fibrillation, (2) valvular abnormalities including post-rheumatic valvular disease, mitral valve prolapse, and a bicuspid aortic valve, and (3) atrial myxomas.

• Temporary vasospasm leading to decreased blood flow can be a cause of amaurosis fugax.^[8][9] Generally, these episodes are brief, lasting no longer that five minutes,^[10] and have been associated with exercise.^[4][11] 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 rentinal vasculature of one eye.”^[10]

• 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.^[12] One comprehensive review found a two to nineteen percent incidence of amaurosis fugax among these patients.^[13]

• Systemic lupus erythematosus^[14][15]

• Periarteritis nodosa^[16]

• Eosinophilic vasculitis^[17]

• Hyperviscosity syndrome^[18]
  • Polycythemia^[19]

• Hypercoagulability^[20]
  • Protein C deficiency^[21]
  • Antiphospholipid antibodies^[22]
    • Anticardiolipin antibodies^[23]
    • Lupus anticoagulant^[24][25]

• Thrombocytosis^[23]

• Subclavian steal syndrome

• Malignant hypertension can cause ischemia of the optic nerve head leading to transient monocular visual loss.^[26]

• Drug abuse-related intravascular emboli^[2]

• Iatrogenic: Amaurosis fugax can present as a complication following carotid endarterectomy, carotid angiography, cardiac catheterization, and CABG surgery.^[23]

Ocular causes include:

• Iritis^[27]
• Keratitis^[18]
• Blepharitis^[18]
• Optic disc drusen^[23]
• Posterior vitreous detachment^[18]
• Closed-angle glaucoma^[28]
• Transient elevation of intraocular pressure^[2][27]
• Intraocular hemorrhage^[2]
• Coloboma^[23]
• Myopia^[23]
• Orbital hemangioma^[29]
• Orbital osteoma^[30]
• Keratoconjunctivitis sicca^[23]

Neurological causes include:

• Optic neuritis^[2]

• Compressive optic neuropathies^[2][23]

• Papilledema: “The underlying mechanism for visual obscurations in all of these patients appear to be transient ischemia of the optic nerve head consequent to increased tissue pressure. Axonal swelling, intraneural masses, and increased influx of 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.”^[31] 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.”^[32]

• Migrane^{[33][34][35][36][37][38][39][40]}

• Pseudotumor cerebri^[41]

• Intracranial tumor^[41]

• Psychogenic^[18]

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor-In-Chief: Marcelo R. Zacarkim, M.D. [2]

Amaurosis fugax is a symptom of carotid artery disease. It occurs when a piece of plaque in a carotid artery breaks off and travels to the retinal artery in the eye. The carotid arteries provide the main blood supply to the brain. They are located on each side of the neck under the jaw. Plaque is a hard substance that forms when fat, cholesterol^[1], and other substances build up in the walls of arteries. Pieces of plaque can block blood flow. In people with amaurosis fugax, vision loss continues as long as the blood supply to the retinal artery is blocked. Atherosclerosis of the arteries in the neck is the main risk factor for this condition. Risk factors for atherosclerosis include heart disease, high cholesterol, smoking, diabetes, and high blood pressure^[2].

• Atherosclerosis

• Diabetes mellitus
• Hypertension
• Transient ischemic attack

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Leber’s congenital amaurosis is an inherited disease resulting in severe vision loss or blindness that was first described by Theodore Leber in the 19th century. Amaurosis can also occur in ruminants suffering from a vitamin B1 (Thiamin) deficiency due to Thiamine-Related Cerebrocortical Necrosis (CCN).

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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In a small minority of those who experience amaurosis, stroke or vision loss has resulted. Diabetes, hypertension and smoking are factors known to increase the risks of suffering this condition. It also can be the result of surgical repair to the mitral valve, when very small emboli may break away from the site of the repair, while the patient’s tissue grows to cover the plastic annuloplasty band.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

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