Amaurosis fugax

Infobox_Disease
Name = Amaurosis fugax

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Caption = The arteries of the choroid and iris. The greater part of the sclera has been removed.
DiseasesDB = 501
ICD10 = ICD10|G|45|3|g|40
ICD9 = ICD9|362.34
ICDO =
OMIM =
MedlinePlus = 000784
eMedicineSubj = neuro
eMedicineTopic = 480
MeshID = D020757

Amaurosis fugax (Latin "fugax" meaning "fleeting", Greek "amaurosis" meaning "darkening", "dark", or "obscure") is a transient monocular visual loss.Fisher, C. "'Transient monocular blindness' versus 'amaurosis fugax.'" "Neurology." 1989;39(12):1622-4. PMID 2685658.]

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."Burde RM. "Amaurosis fugax. An overview." "J Clin Neuroophthalmol." 1989 Sep;9(3):185-9. PMID 2529279] 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.The Amaurosis Fugax Study Group. [http://stroke.ahajournals.org/cgi/reprint/21/2/201.pdf "Current management of amaurosis fugax."] "Stroke." 1990;21(2):201-208.] 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 neuropathies, giant cell arteritis, angle-closure glaucoma, increased intracranial pressure, orbital compressive disease, a steal phenomenon, and blood hyperviscosity or hypercoagulability."Newman NJ. "Cerebrovascular disease." "Walsh & Hoyt's Clinical Neuro-Ophthalmology." (Miller NR, Newman NJ, eds.) Vol 3. 5th ed. Baltimore, Williams & Wilkins; 1998:3420-3426.]

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 artery, or ciliary artery blood flow, leading to a decrease in retinal circulation which, in turn, causes retinal hypoxia. [http://archopht.ama-assn.org/cgi/content/extract/120/2/220 "Exercise-Induced Vasospastic Amaurosis Fugax."] "Arch Ophthalmol." 2002 February;120(2):220-222.] 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 athero-emboli is an atherosclerotic carotid artery.Braat, Andries; Peter H. Hoogland, A.C. DeVries, J.C. Alexander de Mol VanOtterloo. [http://ves.sagepub.com/cgi/content/abstract/35/2/141 "Amaurosis Fugax and Stenosis of the Ophthalmic Artery."] "Vascular and Endovascular Surgery." 2001;35(2):141-142.]
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.Kaiboriboon K; Piriyawat P; Selhorst JB. "Light-induced amaurosis fugax." "Am J Ophthalmol." 2001 May;131(5):674-6. PMID 11336956.] "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."AU Furlan AJ; Whisnant JP; Kearns TP. "Unilateral visual loss in bright light. An unusual symptom of carotid artery occlusive disease." "Arch Neurol." 1979 Nov;36(11):675-6. PMID 508123.]

*Atherosclerotic ophthalmic artery: 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 myxomas.

*Temporary vasospasm leading to decreased blood flow can be a cause of amaurosis fugax.Ellenberger C Jr., Epstein AD. "Ocular complications of atherosclerosis: what do they mean?" "Semin Neurol." 1986;6:185-193.] Fisher M. "Transient monocular blindness associated with hemiplegia." "Arch Ophthalmol." 1952;47:167-203.] Generally, these episodes are brief, lasting no longer that five minutes,Burger, Stephen; robert Saul, John Selhorst, Stephen Thurston. "Transient monocular blindness caused by vasospasm." "The New England Journal of Medicine." 1991;325:870-873.] and have been associated with exercise.Imes RK, Hoyt WF. "Exercise-induced transient visual events in young healthy adults." "J Clin Neuro Ophthalmol." 1989:9;9:178-180.] 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.AU Hayreh SS; Podhajsky PA; Zimmerman B. "Occult giant cell arteritis: ocular manifestations." "Am J Ophthalmol." 1998 Apr;125(4):521-6. PMID 9559738.] One comprehensive review found a two to nineteen percent incidence of amaurosis fugax among these patients.Goodman BW Jr. "Temporal arteritis." "Am J Med." 1979;67:839-852.]

*Systemic lupus erythematosusGiorgi, Afeltra, Gabrieli. "Transient visual symptoms in systemic lupus erthematosus and antiphospholipid syndrome." "Ocular Immunology and Inflammation." March 2001;9(1):49-57.] Gold D, Feiner L, Henkind P. "Retinal arterial occlusive disease in systemic lupus erythematosus." "Arch Ophthalmol." 1977;95:1580-1585.]

*Periarteritis nodosaNewman NM, Hoyt WF, Spencer WH. "Macula-sparing blackouts: clinical and pathologic investigations of intermittent choroidal vascular insufficiency in a case of periarteritis nodosa." "Arch Ophthalmol." 1974; 91:367-370.]

*Eosinophilic vasculitisSchwartz ND, So YT, Hollander H, Allen S, Fye KH. "Eosinophilic vasculitis leading to amaurosis fugax in a patient with acquired immunodeficiency syndrome." "Arch Intern Med." 1986;146:2059-2060]

*Hyperviscosity syndrome
**PolycythemiaBerdel, Theiss, Fink, Rastetter. "Peripheral arterial occlusion and amaurosis fugax as the first manifestation of polycythemia vera." "Journal Annals of Hematology." 1984;48(3):177-180.]

*HypercoagulabilityMundall, Quintero, von Kaulla, Harmon, Austin. "Transient monocular blindness and increased platelet aggregability treated with aspirin." "Neurology." 1972;22:280-285.]
**Protein C deficiencySmith. "Protein C deficiency: A cause of amaurosis fugax?" "Neurol Neurosurg Psychiatry." 1987;50:361-362.]
**Antiphospholipid antibodiesDigre, Durcan, Branch, Jacobson, Varner, Baringer. "Amaurosis fugax associated with antiphospholipid antibodies." "Ann Neurol." 1989;25:228-232.]
***Anticardiolipin antibodies
***Lupus anticoagulantLandi, Calloni, Sabbadini, Mannucci, Candelise. "Recurrent ischemic attacks in two young adults with lupus anticoagulants." "Stroke." 1983;14:377-379.] Elias M, Eldor A. "Thromboembolism in patients with the 'lupus'-type circulating anticoagulant." "arch Intern Med." 1984;144:510-515.]

*Thrombocytosis

*Subclavian steal syndrome

*Malignant hypertension can cause ischemia of the optic nerve head leading to transient monocular visual loss.Hayreh SS, Servais GE, Virdi PS. "Fundus lesions in malignant hypertension, V. hypertensive optic neuropathy." "Ophthalmology." 1986;93:74-87.]

*Drug abuse-related intravascular emboli

*Iatrogenic: Amaurosis fugax can present as a complication following carotid endarterectomy, carotid angiography, cardiac catheterization, and cardiac bypass.

Ocular origin

Ocular causes include:
*IritisSorensen PN. "Amaurosis fugax. A unselected material." "Acta Ophthalmol (Copenh)." 1983 Aug;61(4):583-8. PMID: 6637419.]
*KeratitisBacigalupi, Michael. [http://ijahsp.nova.edu/articles/vol4num2/Bacigalupi.pdf "Amaurosis Fugax-A Clinical Review."] "The Internet Journal of Allied Health Sciences and Practice." April 2006;4(2):1-6.]
*Blepharitis
*Optic disc drusen
*Posterior vitreous detachment
*Closed-angle glaucomaRavits J, Seybold M. "Transient monocular visual loss from narrow-angle glaucoma." "Arch Neurol." 1984;41:991-993.]
*Transient elevation of intraocular pressure
*Intraocular hemorrhage
*Coloboma
*Myopia
*Orbital hemangiomaBrown GC, Shields JA. "Amaurosis fugax secondary to presumed cavernous hemangioma of the orbic." "Ann Ophthalmol." 1981;13:1205-12O9.]
*Orbital osteomaWilkes SR, Troutmann JC, DeSanto LW, Campbell RJ. "Osteoma. An unusual cause of amaurosis fugax." "Mayo Clin Proc." 1979;54:258-260.]
*Keratoconjunctivitis sicca

Neurologic origin

Neurological causes include:
*Optic neuritis

*Compressive optic neuropathiesDigre, Kathleen. [http://intl.elsevierhealth.com/e-books/pdf/783.pdf "Amaurosis Fugax and Not So Fugax—Vascular Disorders of the Eye."] "Practical Viewing of the Optic Disc." Butterworth Heinemann: November 2002:269-344.]

*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."AU Hayreh SS; Podhajsky PA; Zimmerman B. "Transient visual obscurations with elevated optic discs." "Ann Neurol." 1984 Oct;16(4):489-94. PMID 6497356.] 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."AU Smith KJ; McDonald WI. "The pathophysiology of multiple sclerosis: the mechanisms underlying the production of symptoms and the natural history of the disease." "Philos Trans R Soc Lond B Biol Sci." 1999 October 29;354(1390):1649-73. PMID 10603618.]

*MigraineMattsson, Lundberg. "Characteristics and prevalence of transient visual disturbances indicative of migraine visual aura." "Cephalalgia." June 1999;19(5):447.] Cologno, Torelli, Manzoni. "Transient vidual disturbances during migraine without aura attacks." "Headache." October 2002;42(9):930-933.] Connor RCR. "Complicated migraine: A study of permanent neurological and visual defects caused by migraine." "Lancet." 1962;2:1072-1075.] Carroll D. "Retinal migraine." "Headache." 1970;10:9-13.] McDonald WI, Sanders MD. "Migraine complicated by ischemic papillopathy." "Lancet." 1971;2:521-523.] Wolter JR, Burchfield WJ. "Ocular migraine in a young man resulting in unilateral transient blindness and retinal edema." "Pediatr Ophthalmol." 1971;8:173-176.] Kline LB, Kelly CL. "Ocular migraine in a patient with cluster headaches." "Headache." 1980;20:253-257.] Corbett JJ. "Neuro-ophthalmologic complications of migraine and cluster headaches." "Neurol Clin." 1983;l:973-995.]

*Pseudotumor cerebri

*Intracranial tumorHedges, Thomas. [http://stroke.ahajournals.org/cgi/reprint/15/5/907.pdf "The Terminology of Transient Visual Loss Due to Vascular Insufficiency."] "Stroke." 1984; 15(5):907-908.]

*Psychogenic

ymptoms

The experience of amaurosis fugax is classically described as a transient monocular vision loss that appears as a "curtain 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."Beneficial effect of carotid endarterectomy in symptomatic patients with high-grade carotid stenosis." "N Engl J Med." 1991 August 15;325(7):445-53. PMID 1852179.] Other descriptions of this experience include a monocular blindness, dimming, fogging, or blurring.Lord RS. "Transient monocular blindness." "Aust N Z J Ophthalmol." 1990 Aug;18(3):299-305. PMID 2261177.] 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.Donders RC. "Clinical features of transient monocular blindness and the likelihood of atherosclerotic lesions of the internal carotid artery." "J Neurol Neurosurg Psychiatry." 2001 Aug;71(2):247-9. PMID 11459904.] 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 physician immediately as it is a symptom that usually heralds serious vascular events, including stroke.Benavente, Eliasziw, Steifler, Fox, et al. "Prognosis after transient monocular blindness associated with carotid-artery stenosis." "N Engl J Med." 2001;345(15):1084-1090.] Rothwell, Warlow. "Timing of TIA's preceding stroke: time window for prevention is very short." "Neurology." 2005;64:817.] 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.Smit, Ronald; G. Seerp Baarsma and Peter J. Koudstaal [http://www.iovs.org/cgi/reprint/1/1/136.pdf "The source of embolism in amaurosis fugax and retinal artery occlusion."] "International Ophthalmology." 1994 March;18(2):83-86. ISSN 0165-5701.] 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, Holler 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.Walsh J, Markowitz I, Kerstein MD. "Carotid endarterectomy for amaurosis fugax without angiography." "Am J Surg." 1986 Aug;152(2):172-4. PMID 3526933.]

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, aspirin 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."Bernstein EF, Dilley RB. "Late results after carotid endarterectomy for amaurosis fugax." "J Vasc Surg." 1987 Oct;6(4):333-40. PMID 3656582.] If the full diagnostic workup is completely normal, patient observation is recommended.

ee also

*Ocular ischemic syndrome
*Amaurosis

Footnotes