Amaurosis fugax
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| ICD-10 | G45.3 |
|---|---|
| ICD-9 | 362.34 |
Amaurosis fugax (Greek: fugax meaning fugitive, amaurosis meaning darkening, dark, or obscure) is a painless, temporary loss of vision in one eye caused by decreased blood flow (ischemia) to the retina. It is a type of transient ischaemic attack (TIA). The lack of blood flow can be caused by emboli (moving clots) obstructing blood flow in the retinal artery or ophthalmic artery. The most common causes are a clot of plaque or a blood clot from a stenosed carotid artery, other sources are heart or heart valves and arterial spasm. Vision loss lasts for the period of time the clot obstructs blood flow. Amaurosis fugax may also be a symptom of temporal arteritis, an inflammation of the vessel wall.
The experience of amaurosis fugax is often described as a "curtain coming down vertically into the field of vision in one eye". Partial or complete vision loss typically lasts only a few seconds but may last minutes or even hours.
This temporary loss of vision occurs in two conditions which cause a temporary reduction in ophthalmic artery pressure: orthostatic hypotension and positive acceleration.<ref>Phelps GK, Phelps CD. "Blood pressure and pressure amaurosis." Invest Ophthalmol. 1975 Mar;14(3):237-40. PMID 1116922.</ref>
Amaurosis fugax is the temporary loss of vision resulting from sudden acceleration, as in aviation.<ref name="Cline">Cline D; Hofstetter HW; Griffin JR. Dictionary of Visual Science. 4th ed. Butterworth-Heinemann, Boston 1997. ISBN 0-7506-9895-0</ref> In these instances, it is frequently called brownout or greyout if partial vision loss occurs, or blackout if there is complete vision loss. Postive acceleration, as experienced by pilots in steep turns or subjects in a centrifuge, results in decreased blood flow and delivery of oxygen to the brain and eyes.<ref name="Duane">DUANE TD, BECKMAN EL, COBURN KR. "Limitation of ocular motility and pupillary dilatation in human beings during positive acceleration." Invest Ophthalmol. 1962 Feb;1:136-41. PMID 13887999.</ref><ref>Patterson, R and RB Rayman. 1998. "Aerospace medicine: effects of gravity, acceleration and microgravity in the aerospace environment." Encyclopaedia of occupational health and safety, 4th ed. p.102.16-102.19.</ref> The primary cause for visual loss in this event occurs due to decreased retinal circulation which in turn causes retinal hypoxia.<ref name="Duane"/>
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[edit] Management
Despite the temporary nature of the blindness, 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.
[edit] References
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