Scotoma in migraine. Abstract illustration of a migraine headache and associated visual disturbance, or scotoma". Migraines are recurrent throbbing headaches that characteristically affect one side of the head. In some sufferers a visual disturbance called a scotoma occurs just before the attack. This typically appears as a slowly expanding area of blindness surrounded by an irregular, sparkling edge that occupies up to half the visual field. The scotoma clears up after about 20 minutes and is followed by a severe, one- sided headache accompanied by nausea and vomiting. The best therapy is prevention by avoiding any known triggers."