My wife wears prescription bifocal glasses, and the frames she bought last time had sunglass "subframes (?)" that attach in front of her regular frames with a little magnet at each temple hinge. Sort of a modern adaptation of the old clip-on sunglasses. She likes 'em, so maybe the next time you have your frames and glasses updated you might ask about them.

Personally I wear hard gas permeable contacts - they're the only ones that can be made in a prescription strong enough to correct for my nearsightedness and astygmatism - and have no problems for the most part. I put 'em in when I get up in the morning, and take 'em off when I go to bed. I wear dollar-store reading glasses for close work, and sungalsses from Lowes or Home Depot (no Oakleys for this cheapskate!). A pair of clear safety glasses from the same source works for evening or cloudy-day riding when all I need is something to keep the wind out of my eyes - the contacts are prone to drying out in the wind, and it's good to keep bugs and wind-born grit out of the eyes when wearing contacts.