Do photochromic lenses block UV rays?
Do photochromic lenses have UV protection?
Photochromic lenses, known for their unique ability to darken in sunlight, almost always shield your eyes from the harmful effects of the sun's harmful ultraviolet (UV) rays. Double check with the manufacturer to be sure, though.
Why is blocking UV rays important?
The sun’s UV radiation is the same thing that causes sunburns on your skin. UV rays also can cause a sort of sunburn on your eyes, called photokeratitis, which can lead to temporary eye redness, blurry vision, light sensitivity and excessive tearing.
The bigger concern, though, is long-term damage from the sun's UV rays.
Damage to your eyes caused by UV radiation can be easily prevented with the proper protection.
SEE RELATED: What are photochromic sunglasses?
How do photochromic lenses provide UV protection?
The science behind light-to-dark transition lenses also explains how photochromic lenses block UV rays.
A special light-sensitive photochromic coating is applied to eyeglasses and sunglasses with polycarbonate lenses.
Once the coating is applied to the lens, it’s heated, and the chemical enters through microscopic openings in the lens that get bigger with heat. Once the lens cools, the openings shrink back down and the chemical settles, becoming one with the lens.
The chemical solution involved is transparent, so it can be applied to clear eyeglasses and dark sunglasses. When UV radiation comes into contact with a lens treated with this chemical, it can’t pass through.
As a result, photochromic lenses safely reflect UV rays away from the eyes.
It’s important to note that just because a lens is darker, that doesn’t necessarily mean it blocks more UV.
Extremely dark lenses that don’t block ultraviolet light put your eyes at much greater risk than clear, UV-protected eyeglasses. Darkened lenses cause the eyes’ pupils to open wider, meaning the lack of UV protection allows more radiation to enter the vulnerable eyes.
But with proper UV protection — almost always included with photochromic lenses — you can step into the sun and relax, knowing your eyes are fully protected.
LIGHT TO DARK AND PROTECTION FROM UV RAYS, TOO? Shop for photochromic lenses at an optical shop near you or an online eyewear retailer.
Page published in April 2020
Page updated in January 2021