OK, with a scope I close my left eye, with a holo sight or red dot on a rifle both eyes are open. I feel I am more accurate shooting a handgun with both eyes open. It takes a while to get use to this but for me it is the only way to go. Better depth perception, wider field of view and let's face it we don't walk around with one eye closed. I often wondered what happens in an actual self defense situation. Does the shooter even remember if he closed one eye or not?