Serengeti pistoia sungalsses serengeti pioneered photochromic technology and also engineer it into every lens that they make in bright conditions when uv radiation is more intense the lens molecules expand in size darkening the lenses and allowing them to absorb more light in darker conditions when uv radiation is less intense the molecules shrink and separate letting additional light pass through in this way photochromic lenses do the work for your eyes providing the optimal amount o