I have my everyday glasses made with polycarbonate lenses - Varilux progressives because I have really bad eyes and I'm over 50. Ask your eye doc if they can make your prescription in polycarbonate that's thick enough in the center to meet the safety standard. Polycarb is what they use in safety glasses. And pay for the extra scratchproofing.
The tradeoff is you don't get side protection, but you do get protection every minute of the day no matter what you're doing - power tools, hammering, messing with gun springs and recoil plugs, etc.
If you can afford the expensive Flexon frames by Marchon you will end up with super light glasses that spring back when you sit on them - or after clamping muffs on your head. And a real benefit is that you'll get a great seal over the frames when you wear muffs. I started wearing glasses in 1960 and I'm a believer.
www.marchon.com/htmls_2004/flexon.html
"Flexon frames return to shape even after accidental bending occurs. Crafted with a titanium based alloy developed by the US Naval Ordnance Lab, Flexon is made from one of the most flexible metals in the world. With four exclusive patents on Flexon, Marchon is able to offer the wearer superior eyewear that provides comfort, durability and functionality that only a technologically superior product can deliver."
It's true. You can wrap them all the way around your finger - full circle plus some - and they spring right back. IIRC they told me you can do the full wrap demonstration about 200 times. I've been using my frames for 6 years and they still grab my head and never require bending and adjusting to maintain the fit.
John
