You can get Spex as prescription lenses, you have to have your Doc send them a scrip. Contact them directly, not through Overton's for the Rx lenses. That's what my hubby did for his. He has since switched to contacts and the regular Spex, though, which is what I've been doing all along. Much cheaper this way.
Only lost a lens once, years ago, in 10 years of riding with this combo. I keep spares with me. Still have some trouble seeing through water spots, but Sea Drops work well to minimize this. I got it from Campmor.com for a few bucks. I have friends that use contacts and cheap sunglasses. Most of us now wear helmets when we ride and the Spex will go on underneath the helmet if you're careful putting the helmet on. Helmet also holds the sunglasses on fairly well if you have a strap on them.
Sharon