Mild lumen narrowing due to non-calcified plaque refers to the formation of non-calcified plaque in the arteries that blocks the lumen and causes less than 50% of the lumen to narrow. Non-calcified plaques are non-calcified because they contain mainly collagen fibers, smooth muscle tissue and little calcium. Non-calcified plaques are more prone to rupture than calcified plaques, thus causing embolization of the distal lumen. This can cause, for example, cerebral embolism, which can lead to stroke, hemiparesis, aphasia, and sensory deficits. It may also cause ophthalmic artery embolism, leading to ipsilateral blindness. When non-calcified plaques block the lumen of a blood vessel, it is important to treat them under medical supervision in a timely manner to avoid their dislodgment and resulting embolism.