People who smoke more than 20 cigarettes a day risk damage to their vision, a new study has shown. "Cigarette smoke consists of numerous compounds that are harmful to health. It has been linked to a reduction in the thickness of layers in the brain, and to brain lesions, involving areas such as the frontal lobe, which plays a role in voluntary movement and control of thinking, and a decrease in activity in the area of the brain that processes vision," said Steven Silverstein, director of research at Rutgers University's Behavioural Health Care unit.