Amaurosis fugax
Encyclopedia
Amaurosis fugax is a transient monocular visual loss.
), "some of the more frequent causes include atheromatous disease of the internal carotid or ophthalmic artery, vasospasm, optic neuropathies, giant cell arteritis, angle-closure glaucoma, increased intracranial pressure, orbital compressive disease, a steal phenomenon, and blood hyperviscosity or hypercoagulability."
, or ciliary artery
blood flow, leading to a decrease in retinal circulation which, in turn, causes retinal hypoxia. Also, it must be noted that while, 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.
coming down vertically into the field of vision
in one eye;" however, this altitudinal visual loss is relatively uncommon. In one study, only 23.8 percent of patients with transient monocular vision loss experienced the classic "curtain" or "shade" descending over their vision. Other descriptions of this experience include a monocular blindness, dimming, fogging, or blurring. Total or sectorial vision loss
typically lasts only a few seconds, but may last minutes or even hours. Duration depends on the etiology of the vision loss. Obscured vision due to papilledema may last only seconds, while a severely atherosclerotic carotid artery may be associated with a duration of one to ten minutes. Certainly, additional symptoms may be present with the amaurosis fugax, and those findings will depend on the etiology of the transient monocular vision loss.
immediately as it is a symptom
that usually heralds serious vascular events, including stroke
. Restated, “because of the brief interval between the transient event and a stroke or blindness from temporal arteritis, the workup for transient monocular blindness should be undertaken without delay.” If the patient has no history of giant cell arteritis, the probability of vision preservation is high; however, the chance of a stroke reaches that for a hemispheric TIA. Therefore, investigation of cardiac disease is justified.
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 consult 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 etiology is suspected based on the history and physical, additional relevant labs should be ordered.
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, noninvasive 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. With that being the case, researchers investigated how best to evaluate these episodes of vision loss, and concluded that for patients ranging from 36–74 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)." Additionally, concomitant head CT or MRI imaging is also recommended to investigate the presence of a “clinically silent cerebral embolism.”
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 is not advisable in the presence of a normal ultrasound and CT.
is indicated, and a carotid endarterectomy
if the stenosis is surgically accessible. 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." If the full diagnostic workup is completely normal, patient observation is recommended.
Pathophysiology and etiology
Prior to 1990, amaurosis fugax could, "clinically, be divided into four identifiable symptom complexes, each with its underlying pathoetiology: embolic, hypoperfusion, angiospasm, and unknown". In 1990, the causes of amaurosis fugax were better refined by the Amaurosis Fugax Study Group, which has defined five distinct classes of transient monocular blindness based on their supposed cause: embolic, hemodynamic, ocular, neurologic, and idiopathic (or "no cause identified") Concerning the pathology underlying these causes (except idiopathicIdiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
), "some of the more frequent causes include atheromatous disease of the internal carotid or ophthalmic artery, vasospasm, optic neuropathies, giant cell arteritis, angle-closure glaucoma, increased intracranial pressure, orbital compressive disease, a steal phenomenon, and blood hyperviscosity or hypercoagulability."
Embolic and hemodynamic origin
With respect to embolic and hemodynamic causes, this transient monocular visual loss ultimately occurs due to a temporary reduction in retinal artery, ophthalmic arteryOphthalmic artery
The ophthalmic artery is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges...
, or ciliary artery
Ciliary arteries
The ciliary arteries are divisible into three groups, the long posterior, short posterior, and the anterior.* The short posterior ciliary arteries from six to twelve in number, arise from the ophthalmic as it crosses the optic nerve....
blood flow, leading to a decrease in retinal circulation which, in turn, causes retinal hypoxia. Also, it must be noted that while, most commonly, emboli causing amaurosis fugax are described as coming from an atherosclerotic carotid artery
Carotid artery
Carotid artery can refer to:* Common carotid artery* External carotid artery* Internal carotid artery...
, any emboli arising from vasculature preceding the retinal artery, ophthalmic artery
Ophthalmic artery
The ophthalmic artery is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges...
, or ciliary arteries
Ciliary arteries
The ciliary arteries are divisible into three groups, the long posterior, short posterior, and the anterior.* The short posterior ciliary arteries from six to twelve in number, arise from the ophthalmic as it crosses the optic nerve....
may cause this transient monocular blindness.
- Atherosclerotic carotid arteryCarotid arteryCarotid artery can refer to:* Common carotid artery* External carotid artery* Internal carotid artery...
: Amaurosis fugax may present as a type of transient ischemic attackTransient ischemic attackA transient ischemic attack is a transient episode of neurologic dysfunction caused by ischemia – either focal brain, spinal cord or retinal – without acute infarction...
(TIA), during which an embolusEmbolismIn medicine, an embolism is the event of lodging of an embolus into a narrow capillary vessel of an arterial bed which causes a blockage in a distant part of the body.Embolization is...
unilaterally obstructs the lumen of the retinal artery or ophthalmic arteryOphthalmic arteryThe ophthalmic artery is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges...
, causing a decrease in blood flow to the ipsilateral retina. The most common source of these athero-emboli is an atherosclerotic carotid artery.
However, a severely atherosclerotic carotid arteryCarotid arteryCarotid artery can refer to:* Common carotid artery* External carotid artery* Internal carotid artery...
may also cause amaurosis fugax due to its stenosisStenosisA stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
of blood flow, leading to ischemia when the retina is exposed to bright light. "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."
- Atherosclerotic ophthalmic arteryOphthalmic arteryThe ophthalmic artery is the first branch of the internal carotid artery distal to the cavernous sinus. Branches of the OA supply all the structures in the orbit as well as some structures in the nose, face and meninges...
: Will present similarly to an atherosclerotic internal carotid artery.
- Cardiac emboli: Thrombotic emboli arising from the heart may also cause luminal obstruction of the retinal, ophthalmic, and/or ciliary arteries, causing decreased 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 myxomaAtrial myxomaAn atrial myxoma is a benign tumor found in the heart, commonly in the upper left or right side. It grows on the wall that separates the two sides of the heart.-Causes:Myxomas are the most common type of primary heart tumor....
s.
- Temporary vasospasmVasospasmVasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death . Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to...
leading to decreased blood flow can be a cause of amaurosis fugax. Generally, these episodes are brief, lasting no longer that five minutes, and have been associated with exercise. 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."
- Giant cell arteritis: Giant cell arteritis can result in granulomatous inflammation within the central rentinal 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. One comprehensive review found a two to nineteen percent incidence of amaurosis fugax among these patients.
- Systemic lupus erythematosusSystemic lupus erythematosusSystemic lupus erythematosus , often abbreviated to SLE or lupus, is a systemic autoimmune disease that can affect any part of the body. As occurs in other autoimmune diseases, the immune system attacks the body's cells and tissue, resulting in inflammation and tissue damage...
- Periarteritis nodosa
- EosinophilicEosinophiliaEosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds 0.45×109/L . A marked increase in non-blood tissue eosinophil count noticed upon histopathologic examination is diagnostic for tissue eosinophilia. Several causes are known, with the most common being...
vasculitisVasculitisVasculitis refers to a heterogeneous group of disorders that are characterized by inflammatory destruction of blood vessels. Both arteries and veins are affected. Lymphangitis is sometimes considered a type of vasculitis...
- Hyperviscosity syndromeHyperviscosity syndromeHyperviscosity syndrome is a group of symptoms triggered by increase in the viscosity of the blood. Symptoms of high blood viscosity include spontaneous bleeding from mucous membranes, visual disturbances due to retinopathy, and neurologic symptoms ranging from headache and vertigo to seizures and...
- PolycythemiaPolycythemiaPolycythemia is a disease state in which the proportion of blood volume that is occupied by red blood cells increases...
- Polycythemia
- Hypercoagulability
- Protein C deficiencyProtein C deficiencyProtein C deficiency is a rare genetic trait that predisposes to thrombotic disease. It was first described in 1981. The disease belongs to a group of genetic disorders known as thrombophilias. The prevalence of protein C deficiency has been estimated to about 0.2% to 0.5% of the general population...
- Antiphospholipid antibodies
- Anticardiolipin antibodies
- Lupus anticoagulantLupus anticoagulantLupus anticoagulant is an immunoglobulin that binds to phospholipids and proteins associated with the cell membrane. It is important to note that this disease name is actually a misnomer...
- Protein C deficiency
- ThrombocytosisThrombocytosisThrombocytosis is the presence of high platelet counts in the blood, and can be either primary or reactive...
- Subclavian steal syndromeSubclavian steal syndromeIn medicine, subclavian steal syndrome , also called subclavian steal phenomenon or subclavian steal steno-occlusive disease, is a constellation of signs and symptoms that arise from retrograde flow of blood in the vertebral artery or the internal thoracic artery, due to a proximal stenosis ...
- Malignant hypertensionMalignant hypertensionMalignant hypertension or hypertensive emergency is severe hypertension with acute impairment of an organ system and the possibility of irreversible organ-damage...
can cause ischemia of the optic nerve head leading to transient monocular visual loss.
- Drug abuse-related intravascular emboli
- Iatrogenic: Amaurosis fugax can present as a complication following carotid endarterectomyCarotid endarterectomyCarotid endarterectomy is a surgical procedure used to prevent stroke, by correcting stenosis in the common carotid artery...
, carotid angiography, cardiac catheterizationCardiac catheterizationCardiac catheterization is the insertion of a catheter into a chamber or vessel of the heart. This is done for both investigational and interventional purposes...
, and cardiac bypass.
Ocular origin
Ocular causes include:- IritisIritisIritis is a form of anterior uveitis and refers to the inflammation of the iris of the eye.-Types:There are two main types of iritis: acute and chronic. They differ in numerous ways....
- KeratitisKeratitisKeratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...
- BlepharitisBlepharitisBlepharitis is an ocular condition characterized by chronic inflammation of the eyelid, the severity and time course of which can vary. Onset can be acute, resolving without treatment within 2–4 weeks , but more generally is a long standing inflammation varying in severity...
- Optic disc drusenOptic disc drusenOptic disc drusen or optic nerve head drusen are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc...
- Posterior vitreous detachmentPosterior vitreous detachmentA posterior vitreous detachment is a condition of the eye in which the vitreous humour separates from the retina.Broadly speaking, the condition is common for older adults and over 75% of those over the age of 65 develop it. Although less common among people in their 40s or 50s, the condition is...
- Closed-angle glaucomaGlaucomaGlaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
- Transient elevation of intraocular pressure
- Intraocular hemorrhage
- ColobomaColobomaA coloboma is a hole in one of the structures of the eye, such as the iris, retina, choroid or optic disc...
- MyopiaMyopiaMyopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...
- Orbital hemangiomaHemangiomaA hemangioma of infancy is a benign self-involuting tumor of endothelial cells, the cells that line blood vessels. It usually appears during the first weeks of life and sometimes resolves by age 10. In more severe case hemangioma may have permanency, if not treated by a physician...
- Orbital osteomaOsteomaAn osteoma is a new piece of bone usually growing on another piece of bone, typically the skull. It is a benign tumor.When the bone tumor grows on other bone it is known as "homoplastic osteoma"; when it grows on other tissue it is called "heteroplastic osteoma".Osteoma represents the most common...
- Keratoconjunctivitis siccaKeratoconjunctivitis siccaKeratoconjunctivitis sicca , also called keratitis sicca, xerophthalmia or dry eye syndrome is an eye disease caused by eye dryness, which, in turn, is caused by either decreased tear production or increased tear film evaporation. It is found in humans and some animals...
Neurologic origin
Neurological causes include:- Optic neuritisOptic neuritisOptic neuritis is the inflammation of the optic nerve that may cause a complete or partial loss of vision.-Causes:The optic nerve comprises axons that emerge from the retina of the eye and carry visual information to the primary visual nuclei, most of which is relayed to the occipital cortex of the...
- Compressive optic neuropathiesOptic neuropathyThe optic nerve contains axons of nerve cells that emerge from the retina, leave the eye at the optic disc, and go to the visual cortex where input from the eye is processed into vision. There are 1.2 million optic nerve fibers that derive from the retinal ganglion cells of the inner retina. Optic...
- PapilledemaPapilledemaPapilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare....
: "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 fluidInterstitial fluidInterstitial fluid is a solution that bathes and surrounds the cells of multicellular animals. It is the main component of the extracellular fluid, which also includes plasma and transcellular 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." Generally, this transient visual loss is also associated with a headache and optic disk swelling.
- Multiple SclerosisMultiple sclerosisMultiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...
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."
- MigraineMigraineMigraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
- Pseudotumor cerebri
- Intracranial tumor
- PsychogenicPsychogenic painPsychogenic pain, also called psychalgia, is physical pain that is caused, increased, or prolonged by mental, emotional, or behavioral factors.Headache, back pain, or stomach pain are some of the most common types of psychogenic pain...
Symptoms
The experience of amaurosis fugax is classically described as a transient monocular vision loss that appears as a "curtainCurtain
A curtain is a piece of cloth intended to block or obscure light, or drafts, or water in the case of a shower curtain. Curtains hung over a doorway are known as portières...
coming down vertically into the field of vision
Visual field
The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...
in one eye;" however, this altitudinal visual loss is relatively uncommon. In one study, only 23.8 percent of patients with transient monocular vision loss experienced the classic "curtain" or "shade" descending over their vision. Other descriptions of this experience include a monocular blindness, dimming, fogging, or blurring. Total or sectorial vision loss
Vision loss
Vision loss or visual loss is the absence of vision where it existed before, which can happen either acutely or chronically .-Ranges of vision loss:...
typically lasts only a few seconds, but may last minutes or even hours. Duration depends on the etiology of the vision loss. Obscured vision due to papilledema may last only seconds, while a severely atherosclerotic carotid artery may be associated with a duration of one to ten minutes. Certainly, additional symptoms may be present with the amaurosis fugax, and those findings will depend on the etiology of the transient monocular vision loss.
Diagnostic evaluation
Despite the temporary nature of the vision loss, those experiencing amaurosis fugax are usually advised to consult a physicianPhysician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
immediately as it is a symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
that usually heralds serious vascular events, including stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
. Restated, “because of the brief interval between the transient event and a stroke or blindness from temporal arteritis, the workup for transient monocular blindness should be undertaken without delay.” If the patient has no history of giant cell arteritis, the probability of vision preservation is high; however, the chance of a stroke reaches that for a hemispheric TIA. Therefore, investigation of cardiac disease is justified.
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 consult 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 etiology is suspected based on the history and physical, additional relevant labs should be ordered.
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, noninvasive 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. With that being the case, researchers investigated how best to evaluate these episodes of vision loss, and concluded that for patients ranging from 36–74 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)." Additionally, concomitant head CT or MRI imaging is also recommended to investigate the presence of a “clinically silent cerebral embolism.”
If the results of the ultrasound and intracranial imaging are normal, “renewed diagnostic efforts may be made,” during which fluorescein angiography
Fluorescein angiography
Intravenous Fluorescein angiography or fluorescent angiography is a technique for examining the circulation of the retina using the dye tracing method...
is an appropriate consideration. However, carotid angiography is not advisable in the presence of a normal ultrasound and CT.
Treatment
If the diagnostic workup reveals a systemic disease process, directed therapies to treat that underlying etiology should be initiated. If the amaurosis fugax is caused by an atherosclerotic lesion, aspirinAspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
is indicated, and a carotid endarterectomy
Carotid endarterectomy
Carotid endarterectomy is a surgical procedure used to prevent stroke, by correcting stenosis in the common carotid artery...
if the stenosis is surgically accessible. 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." If the full diagnostic workup is completely normal, patient observation is recommended.