Hi, i don t think that blindness in your friends daughter is due to Vyvanse, blurring of vision is reported in overdose. At usual doses tics like movement can occur. Other symptoms occurs in overdose like abdominal or stomach crampsblurred, blurred vision, muscle pain or stiffness, nervousness, restlessness, seeing, hearing, or feeling things that are not there, seizures, shakiness in the legs, arms, hands, or feet, sweating, trembling or shaking of the hands or feet, violent actions. I hope this has helped you. Wishing your child good health. Take care.