The eye can be affected by obstructive phenomena within large vessels, such as the corotid arteries, as well as in the ophthalmic artery, central retinal artery, and branch retinal arteries. The visual impairment seen with central retinal vein obstruction usually occurs over a period of days to weeks, and although vision improves spontaneously in some eyes, in others it deteriorates to the same degree as that in eyes with arterial obstruction. Macular degeneration is the leading cause of legal blindness in the US, generally affecting the older population.