If you shoot pistol defensively, you need to do it both eyes open if you can. Don't focus on the target, regardless. Always focus on the front sight. You should be looking at the target/threat, punch or bring the pistol up into your line of sight with a slight upward cant. Your eyes will pick up the frong sight. When this happens, focus on the front sight. You'll still see the target in the background. After you shoot, do it all over again. Don't make a habit of looking for your hits, just re-aquire and shoot again. If you aren't focused on the front sight, you won't be able to maintain good sight picture and you'll likely miss. If you're left eye dominant, just turn your head, don't move the gun as it can cause bad grip and shooting stance and make it harder to control recoil.