What is the definition or description of: aura?

Related to migraine: The term aura is usually used to describe a visual change that occurs at the onset of a classic migraine. It is typically described as an odd light appearance, color change or other visual illusion associated with the headache. Not all migraines have auras..."common migraines" do not have auras, while "classic migraines" do.

Visual or: Disturbed perceptions. Vision is disturbed in migraine headaches. It is the sensation that people with epilepsy experience before the seizure occurs.