Anyone seen ads for prescription glasses that change tint darkness according to !

Anyone seen ads for prescription glasses that change tint darkness according to light levels?

I swear I've seen ads for such a thing, but I cannot find the actual product anywhere! Do these actually exist? What are they called? Where can I find them?

You must be talking about Transitions. I have a pair of them and they do darken outside, but its according to the UV, not the light, which prevents them from changing indoors and also prevents them from getting real dark in the car. Most windows in cars have a UV filter built in, so Transitions won't get as dark as most people would like for sunglasses while driving. I like my Transitions for when I'm in and out. They darken almost immediately as soon as the sun hits them, but it takes longer for them to clear up once you're inside. But for when I'm driving, I have a second set of prescription sunglasses for when my Transitions lenses aren't dark enough.

Years ago, Photogrey Xtra lenses were very popular. These are glass lenses (instead of plastic or ploycarbonate) and they darken according to the light, which means they DO darken inside and they DO darken in your car. The problem with the PGX lenses is that they are extremely heavy, and lenses made of glass at the least safest when it comes to shattering. Most people want their glasses to be comfortable and light weight and glass does not offer that, especially to those who have stronger prescriptions. Where I work, we see a few people who still ask for the old PGX glass lenses because they ARE more durable when it comes to scratching. We have quite a few people who work in foundries, or in environments where they can't really be choosy about what they use to clean their lenses, so they opt for glass because they grab anything to wipe them and they don't scratch.

Ask your eye care professional about Transitions lenses and see if they are right for you...