What does it mean to have a dot of blood in your eye?

Dry eyes?: The vast majority of conjunctival hemorrhages are caused by dry eyes which can be helped with artificial tears. Sometimes, the bleeding can be worsened by use of anticoagulants such as Coumadin (warfarin) or plavix. Other causes include uncontrolled blood pressure and bleeding disorders. If you have headaches or other symptoms, please see your ophthalmologist right away.

Usually nothing: Might be a prominent vessel or a burst vessel on the white part of the eye. If inside the eye (over iris or something), then can be more serious.