I find varifocals are fine for cruise flying and I can actually read the binnacle mounted GPS and instruments while wearing them. However when it comes to final approach I just hate the things and normally take them off as I really don't know where the ground is. Ditto for anything involving hovering. After a few instances when I came into the hover to land and gently went down until I thought I was on the ground, then relaxed on the controls and dropped the last foot like a stone, I now take the things off before attempting it. I find the very low work so much easier without them. I do wear glasses for reading and for driving if I remember, but for very low level flying, no way!