Eyeglasses | Optical Centre Smartbuyglasses ZA

Photochromic Lenses - Lenses That Change Colour

Photochromic lenses, colloquially known at transition lenses, darken when they come in direct contact with UV light. For instance, if you're indoors or in dense shade, the glasses lenses will stay transparent, but if you step into sunlight, they will darken into tinted sunglasses. This makes them a great option for those who don't want to have to swap between glasses and prescription sunglasses.  

What are Photochromic Lenses?

These special lenses react to varying levels of UV light. When they come into contact with very bright lights, molecules in the lenses react and become a darker colour, providing protection from the sun's rays. When light levels drop, however, the molecules go back to their original state and become transparent. Photochromic lenses only react when exposed to UV light, which means that a brightly lit home or office will not cause them to darken. 

How do Photochromic lenses work?

Photochromic lenses are covered in special molecules, such as silver chloride, that adapt to different amounts of UV rays. When it is very bright, for instance, they can change shape and absorb light. This property allows them to transition into sunglasses in the sunlight. However, once they are removed from such direct sunlight, the process reverses and the lenses transition back to their clear state. Lenses will take about 15 minutes to fully darken, though some tint will probably occur in the first few minutes. 

Photochromic Sunglasses

Normal sunglasses that are fitted with photochromic lenses are called photochromic sunglasses. Photochromic glasses usually become sunglasses when you are outside and transition to glasses with transparent lenses when indoors. However, photochromic sunglasses come with already darkened lenses and become even darker. These are usually only meant for outdoor use. However, it should be noted that photochromic lenses should not be worn for driving. As car windshields already come with a UV blocking coating on the windshield, this may interfere with photochromic sunglasses's reading of UV levels. 

Transitions™ Lenses

Photochromic lenses, manufactured by Essilor, Hoya, and ZEISS, are known commercially as "transitions" lenses. 

At SmartBuyGlasses, we carry several models of photochromic sunglasses, such as the best-selling Oakley Radarlock Path, the Rudy Project Magster, and the Serengeti Tosca. If you have any more questions about these lenses, feel free to ask one of our professional opticians!


Still have questions? Feel free to ask our online optician! Find out more here.

Was this article helpful? Thanks for your feedback!