When shooting with my red dot on the .22 I have both eyes open. Now when I'm shooting my CZ with iron sights, the front sight is really blurry no matter how hard I try to focus on it. My left eye wants to see the target, right is trying to focus separately on it...and it just doesn't work.
I may go back to closing left eye or using a flip-down cover when at the range. In a defensive situation there's not gonna be any focusing on sights so that's a moot point.