Changing lenses

I was just watching a commercial and had this idea. It was advertising these glasses that protected your eyes from uv rays that changed their tint. I it got darker thatd start to get like regular clear glasses but the brighter it got outside the dark they would get.I'm sorry I cant explain things very well through typing. But if any of you understood me tell me what you think and also the flaws behind making them or using them. I just thought they'd be useful for games that go from say an open field to dark woods, day-night, or speedball to woodsball where one type of play requires clear vision and the other you may need darker tinted lenses to keep the sun out. I've always wanted mirrored lenses for my dye but dont like dark lenses in the woods so I think these would come in handy.

Those would be pretty cool. I'd also wear them. I want to get a new mask and tinted lenses soon.

i got glasses wit those lense.my look clear as any other regular glasses when not in sun light. and its suxs cause when ur in a car they dont wrk good cause they cant change darker cause ur windsheild is alrdy blocking the uv rays.

i would googles like that