In reply to HeMa:
My idea when I bought the Oakley goggles was that I could swap lenses in the valley based on a prediction of conditions on the mountain. This didn't work, in practice... although that was mostly because the frames were defective so I didn't keep them for long enough to see. I'm looking for a replacement for those (have been borrowing goggles for the last few years) and I am trying to decide whether I should go with swappable lenses, multiple pairs of goggles or photochromatic - hence the question.
I didn't actually know you could get photochromatic lenses until yesterday, when I was browsing gear reviews.
Salomon claim that the lenses also get lighter with colder temperatures. Could they have incorporated that feature to solve the UV problem?
Unfortunately, finding gear reviews of these things is next to impossible through Google - all you get are aggregate sites with meaningless star ratings, listing sellers and prices and discounts and replicating the manufacturer's blurb. All these sites try to LOOK like review sites for SEO purposes but not a one of them features a proper review by a person who actually used the product.