No snakes don't close there eyes they have no eye lids they do have a ocular scale called the brille (eyecap - you can see it when your snake sheds). This brille offers some of the functions of the eyelid. It keeps the eyes moist, protects there eyes from dust etc
so your saying snakes dont sleep they just relax 24/7 and when they r sleeping they can still see you when u walk pass are they kinda like a fish eyes ?
They sleep with there eyes open obviously I think it has something to do with there pupils, look at your snake's when it's sleeping next, touch it watch it's pupil dilate.