Photochromic lenses are eyeglass lenses that are clear (or nearly clear) indoors and darken automatically when exposed to sunlight. Other terms sometimes used for photochromic lenses include “light-adaptive lenses,” “light intelligent” and “variable tint lenses.”
HOW PHOTOCHROMIC LENSES WORK
The molecules responsible for causing photochromic lenses to darken are activated by the sun’s ultraviolet radiation. Because UV rays penetrate clouds, photochromic lenses will darken on overcast days as well as sunny days.
Photochromic lenses typically will not darken inside a vehicle because the windshield glass blocks most UV rays. Recent advancements in technology allow some photochromic lenses to activate with both UV and visible light, providing some darkening behind the windshield
PHOTOCHROMIC LENSES WITH BLUE LIGHT TECHNOLOGY
Besides protecting your eyes from glare outdoors, photochromic lenses offer an additional important benefit — they help protect your eyes from harmful blue light.
Since blue light contributes to digital eye strain and causes oxidative stress in the retina; it’s even possible that long-term exposure to harmful blue light from sunlight and the display screens of computers, smartphones and other digital devices may increase a person’s risk of macular degeneration and other eye problems later in life.