Photochromic lenses, often called transitions or reactolights, darken to a sunglasses tint when exposed to sunlight, or U/V ultraviolet, and return to a clear state when indoors, away from U/V light.
Photochromic lenses are made of many lens materials including plastic, glass or polycarbonate. They are typically used as sunglasses that conveniently switch from a clear lens indoors, to a sunglasses depth tint when outdoors, and vice versa.
They typically take around 30 seconds to fully darken and approx 2 - 5 minutes to return to a clear state.
Photochromic lenses were created in the 1960's at the Corning Glass Works Inc, and became the first variable tint/photochromic lenses brought to the marketplace.
Tiny molecules of silver halide and chloride are embedded within a photochromic lens which is invisible and clear until exposed to sunlight/UV rays. A chemical process takes place when exposed to sunlight/UV and the molecules effectively move, change shape and absorb the light. This process changes the molecules and they darken to a sunglasses shade/tint.
The photochromic lens will remain in this 'darkened' sunglasses state whilst exposed to sunlight/UV and the molecules will reverse the process once the lenses are removed from the sunlight/UV rays returning to the original 'transparent/clear' lens.
Reglazing photochromic lenses and enhancing your visual acuity, colour contrast, visual comfort and also blocking out 100% of harmful UVA and UVB light is as simple as adding it to your lens options when choosing your lenses.
Please don't hesitate to contact us should you require any further information and one of our advisers will be happy to assist you.