For me, rear sight is blurry, front sight less so, target in focus. So, I go with target primary and front sight secondary, thru the distance vision part of my glasses. Works OK out to 15yds or so. I go thru the bifocals after that in order to bring the front sight in focus. Been wearing bifocals for 6-7 years now, am having to mount magnified optics on all my long guns 'cause I can't use the irons any more.
Stu
Stu