If you wear corrective optics might be a good idea to train without them occasionally too... you may not remember or have time to grab your glasses or put in contacts when Things Go Bump In The Night, and I can't really recommend sleeping on your back and never taking 'em off like I do. (Granted, I'm on a round-the-clock schedule so my sleep is 90 minutes a a time rather than straight-through, but... yeah, can't recommend that either.)