Have you ever wondered how Transitions® lenses work? The magical mash-up of sunglasses and eyeglasses, when you see them change color, you feel like – the future is now. Transitions® are an example of photochromic lenses.

Some other names for photochromic lenses are Light Adaptive, Variable Tint, Photochromatic, but many people call just them by the popular name brand Transitions®; you could say they’re the the “Kleenex” of photochromic lenses.

If we start with the etymology of the word, photochromic comes from two Greek words; photo meaning light and chroma meaning color.

Photochromic lenses change color when exposed to light.

You can get clear photochromic eyeglasses that change all the way to dark sunglasses, or photochromic sunglasses which are just for outdoor wear (and do not get completely clear.)

So how do Transitions® lenses work? When exposed to light, the photochromic molecules in the lenses begin to change structure, like in the illustration below. This new arrangement allows the molecules to absorb more light which causes the lenses to darken. Most photochromic lenses to UV light; that’s why they change when you’re in the sun yet remain clear indoors.

how do photochromic lenses work

Temperature also has effect on the reaction time of the molecules in photochromic lenses. On a cold day, your lenses will react more slowly than on a warm day.

In this video, one of FramesDirect.com’s expert opticians, Travis, explains further:


Transitions® lenses continuously adapt to changing light conditions and block 100% percent of harmful UVA and UVB rays. Having your lenses give you the exact amount of protection you need to see clearly, means your eyes are doing less work. And there’s the added benefit of only having one pair of glasses for indoors and out!

Learn more about Transitions lenses