Sunday, March 13, 2011

Amaurosis Fugax

Amaurosis fugax is a pathological condition which is characterized by a transient loss of vision in one eye owing to a temporary lack of blood circulation to the retina. Vision loss lasts from a few seconds to several minutes before recovering the vision in the affected eye. The differential diagnosis for amaurosis fugax can be managed efficiently by categorizing the possible etiologies. Thus, the causes of amaurosis fugax can be embolic, hypoperfusion, ocular, and neurological. When there is an embolic cause, amaurosis fugax could be a symptom of carotid artery disease, which 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.

When evaluating these causes, one can see that the common etiologies for amaurosis fugax are circulatory problems (either embolic or hypoperfusion). 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. Tests include a complete eye and neurological exam. In some cases, an eye exam will reveal a bright spot where the clot is blocking the retinal artery. A carotid ultrasound or magnetic resonance angiography (MRA) scan should be done to evaluate a blockage in the carotid artery.