Photochromic lens were developed at 1960s by William H.Armistead and Stanley Donald Stookey at corning glass works. Photochromic lens is also known as day and light lenses,transition lens ,variable tint ,photo sun lenses.
This lens is designed in such a way that lenses turn dark like sunglasses in the presence of sunlight(ultraviolet rays) and changes back to clear when you walk indoors or when the sun sets .Photochromic lens protects our eyes from the harmful damage that can occur from prolonged exposure to ultraviolet and bluelight .
Indoor – Dim light – Hard light
How they work?
Basically these react to UV light the photochromic molecules in lenses begin to change the structure absorbing more light and finally darkening the lenses. Photochromic lenses are coated with molecules such as silver chloride which change shape and then absorb light when exposed to UV Ray’s .The process reverses when taken away from the sunlight.
- Visual comfort (indoor and outdoor) -Available in single vision ,bifocal and trifocals forms.
- Respond to temperature variations.
- Blocks 100% of the sun’s eye damaging UV rays reducing eye fatigue.
Note: Some photochromic lenses may not be suitable for driving because car windshields are coated with a UV blocking layer which will therefore prevent photochromic lenses from being able to adjust to light conditions inside your car.
-MONIKA MANDAL/CONSULTANT OPTOMETRIST