Adjusting to changing light conditions
Phototropic spectacle lenses detect changing light conditions and react to them.
Just as with polarising spectacle lenses, phototropic spectacle lenses have a special (invisible) layer integrated into the lens, the molecules of which react to different light conditions. When the spectacle lenses are exposed to a lot of light, the molecules become darker, but when less light hits them, they remains clear. That means that, when the sun is shining, after a very short reaction period, these spectacle lenses are just about as dark as regular tinted sunglasses.
Inside, on the other hand, the lenses are as clear as normal non-tinted glass. These lenses do away with the need to constantly switch glasses, making them exceptionally practical.
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