Know why drunk drivers see halos as they zoom past city lights leading to traffic accidents? It's because alcohol disturbs the tear-film that covers the surface of their eyes leading to deterioration of vision. Alcohol consumption markedly impairs night-vision because it increases the perception of halos (luminous circles) and other visual night-time disturbances a new study shows. 'This is because ethanol from alcoholic drinks passes into the tear and disturbs the outermost layer of the tear-film - the lipid layer - facilitating the evaporation of the aqueous part of the tear' said principal author of the study Jose Juan Castro