I am right handed and right eye dominant. I have bad eyesight and wear glasses. I have found that I can shoot with both eyes open only if lighting conditions are right. Too dark, I have to close my left eye. Also, barrel length plays a part. Short barrel - I can have both eyes open. Long barrel handgun and rifles - left eye closed. No matter what, when I bring the gun up to shoot I keep both eyes open until I am ready to aim and at that point I can decide to leave both eyes open but at the range I almost always close my left eye. The same goes for scopes and optics. I nearly always have to close my left eye.