We've all experienced red, bloodshot eyes from time to time, affecting one or both eyes. Red eye is caused by swollen or dilated blood vessels on the sclera, the white outer surface of the eye. Red eyes can be accompanied by eye pain, itching, eye discharge, swollen eyes or visual disturbances such as blurry vision.In other cases, a red eye may cause no irritation at all.ommon Causes of Red Eye. Conjunctivitis. Also called  pink eye , conjunctivitis is one of the most common (and contagious) eye infections, particularly among school children. It occurs when the conjunctiva  the thin, normally transparent membrane that covers the sclera and lines the eyelids  becomes infected.