Where can I get prescription sunglasses that will block harmful rays?

A: I think you need to find a better optician, that's what I think. On the one hand, he or she is right—you want lenses that block both UV and IR. Ideally, your glasses should block 100 percent of UVA and UVB rays (the different bands of UV radiation—UVC rays are of little concern as they are absorbed by Earth's upper atmosphere), and 100 percent IR, too. Also, at high altitude you want visible light cut by 80 to 85 percent.

You don't specifically mention what high-altitude activity you have in mind. If you're mountaineering, then get glacier goggles—their side panels and mount for nose-shields makes them ideal. Julbo's Micropores ($90) are a first-rate glacier glass than can be fitted with prescription lenses. If you want the glasses for all-around use, then a good sports glass would work. Oakley, for instance, will make nearly any of their glasses to order with your prescription. Or, you can retrofit many glasses with prescription lenses.

In either case, ask around for a local optometrist who has some experience with mountaineering and high-altitude stuff. Surely Billings has one. You need more than "might work" for words of recommendation—you need someone who KNOWS what will work.

Good luck!