Hi! alcohol’s effect on on a person's vision causes their eye muscles to relax to the point that they can't focus and their pupils take longer to adjust to changes in light, allowing them to be blinded by the glare of headlights. So that’s the cause of the person vision causes. Also how it would be effect by alcohol effect on a person's vision causes impaired vision on that person, which can cause injury or death to themselves or others if preventative measures are not taken. So I hope that help and explained well :)