When you are out and facing intense glare of light bouncing off from the water or the snow you should were Sunglasses that block blue light rays. Slightly dark foakleys Sunglasses with a slightly green or brown tint will filter out the blue light rays.Photochromatic lenses become darker as the intensity of ultraviolet light increases. That's why they are lighter when indoors. If you want to use photochromatic Sunglasses while driving then choose the fairly dark ones.Mirror lenses reflect most of the light instead of absorbing it. But these lenses get scratched easily. So if you want to buy Sunglasses with mirror lenses buy the ones which have anti scratching coating on them. Nowadays most of the fake oakley sunglasses come with the plastic lenses. These are tougher and more durable than the glass lenses and less likely to shatter. So if you buy the Sunglasses with plastic lenses, buy the lenses which have scratch resistant coating.