Fig. 24.2 Atherosclerotic plaque composed of fibrous tissue, cholesterol and calcium from a patient who underwent endarterectomy (Courtesy of Ms. Karen Albert)

Symptoms

Loss of Vision

Over 90% of patients with the OIS relate a history of visual loss in the affected eye(s) [5]. In twothirds of cases it occurs over a period of weeks to months, while it is abrupt in approximately 12%. In the abrupt vision loss cohort there is often a cherryred spot present on funduscopic examination.

Prolonged recovery following exposure to a bright light has been described in patients with severe carotid artery obstruction [20]. Concurrent attenuation of the visual evoked response after light exposure has also been observed in these cases [20]. With instances of bilateral, severe carotid artery obstruction, the visual loss after exposure to bright light occurs in both eyes, thus mimicking occipital lobe ischemia due to vertebrobasilar disease [21].

Amaurosis Fugax

A history of amaurosis fugax is elicited in about 10% of OIS patients [5]. Amaurosis fugax, or fleeting loss of vision for seconds to minutes, is thought to be predominantly caused by emboli to the central retinal arterial system, although vasospasm may also play a role [22], as can giant cell arteritis [23]. While the majority of people with amaurosis fugax alone do not have the OIS, it can be an indicator of concomitant, ipsilateral carotid artery obstructive disease. Approximately one-third of patients with amaurosis fugax have an ipsilateral carotid artery obstruction of 75% or greater [24]. Rarely, amaurosis fugax has been