Could blocked carotid arteries impair vision?

Definately. Amarosis fugax, or "fleeting blindness" is described as a curtain coming down over your eye -- this is a classic presentation of carotid artery disease. You should see your doctor right away.
Absoltuely. Blocked carotid arteries can cause a number of problems ranging from a slow decrease in the oxygen getting to one eye to a sudden blockage of blood flow from a clot.

Related Questions

Could blocked carotid arteries impair vision?

Yes. It can cause a field cut (homonymous hemianopsia) in which vision is lost in the same area of the field in both eyes often described as "shade coming down"; it can also cause sudden blindness in one eye (retinal embolism). Read more...