noun
photochromic lens
A lens that darkens when exposed to sunlight and clears indoors. Common in eyeglasses and sunglasses.
このメガネはフォトクロミックレンズを使っているので、外に出ると色が濃くなる。
These glasses use photochromic lenses, so they darken when you go outside.
Variant with a middle dot, sometimes used for clarity.
Loanword from English 'photochromic lens'.