It takes about 30 seconds for your clear photochromic lenses to darken, and your lenses may continue to gradually (and subtly) change to an even darker tint during your first 10 minutes outdoors. Once indoors again, photochromic lenses become clear in five minutes or less. 

The exact adjustment time required for these light-sensitive lenses can vary depending on temperature and the amount of ultraviolet (UV) exposure.

How do photochromic lenses work?

Sun-sensitive lenses have specialized dyes embedded or bonded to their surface. These dyes contain molecules that produce a chemical reaction when they come in contact with UV light.

The millions of sunlight-sensitive molecules in each photochromic lens change shape and structure when exposed to UV light. Because photochromic lenses react to UV light, they automatically darken outdoors, even on cloudy days, but not indoors under artificial lighting.

The chemical process that darkens photochromic lenses also depends on factors such as temperature. This explains why Transitions® lenses take longer to darken when it is cold outside. The molecules inside the lens move and change shape more slowly at colder temperatures so that Transitions® lenses can adjust their tint more quickly on hot days.

Transitions® lenses not only adjust their tint to match the light, but they also absorb 100% of UVA and UVB rays, providing total protection from the sun's most damaging rays. Like sunglasses, photochromic lenses can reduce the risk of developing eye conditions such as cataracts, macular degeneration and sunburns of the cornea. 

To learn more about Transitions® photochromic light-sensitive lenses and find the technology that's right for you, schedule an appointment with your trusted optometrist at IRIS.