Because of the fogging issue with goggles, I have over the years worn prescription sunglasses up to and just short of white-out snow. The glasses I have worn for the last 5 years or so are the Julbo Micropores. You can, and I did, buy them at backcountry.com. They have excellent side guards that really prevent eye tearing even at stupid groomer speeds. On delivery, I gave them over to my optician and had the prescription lenses installed; I chose transition lenses so they work at lunch indoors, yet offer good protection even on bright spring days. I have a very near-sighted prescription, about 5.5 diopters per side, and the shallow base curve of the frame accomodates that without distortion. More severely curved, face fitting frames (read: cool) would not go as high.
Of course, I am as much of a powder hound as anyone hanging out here, and struggled for many, many years with goggle solutions. I had hung on to a pair of 20 year old Killy goggles with Rx inserts until 3 years ago when a fellow JH Steep and Deep camper recommended a Smith solution. She was using, and I bought, the Smith Prophecy goggles. Those, and several other models accomodate Smith's Rx insert, which clicks into detents in the goggle nose piece and sit about 1/4" behind the goggle lens. This is just far enough from my eyes that I have had zero fogging issues in the three seasons I have used them, and I've had some epic powder days with them. In addition to the Prophecy goggles, the IO/X goggles have the same detents on the nose piece. A couple of weeks back, Level Nine Sports had the IO goggles at a ridiculously low price, and I sprung for a pair. However, I called ahead to Smith to make sure they had the detents, and it turns out that the IO/Xs do, but the standard IOs do not, nor do the IO/Ss. So, buyer beware. I like the look of the IO/Xs, particularly with my Smith helmet, and am really looking forward to trying them out next time out. BTW, you won't find the Rx inserts in ski shops: you will have to order them from Smith, and can do so on their web site. If needed, you will find their friendly customer service people very helpful. I HIGHLY recommend the all-Smith solution. They say that the goggles are designed together with the helmets to maximize air flow and hence minimize fogging. In my experience, they deliver on that promise.
Settling on this combination finally has me not having to futz with my eyewear on the slopes. Best of all, the guys no longer leave me behind on powder mornings.