A visual aura is a temporary visual disturbance that often occurs before a migraine headache. It can manifest as flashing lights, zigzag lines, or blind spots in a person's field of vision. These symptoms usually last between 20 minutes to an hour and can vary in intensity. Visual auras are part of a condition known as migraine and can affect individuals differently. While not everyone who experiences migraines will have a visual aura, those who do may find it helpful to recognize the signs as a warning for an impending headache.