Photochromic lenses are optical lenses that darken when exposed to high energy light such as ultraviolet (UV). The lenses go back to a clear state when the ultraviolet light does not reach them anymore. The lenses are able to get darker even during a cloudy day as UV can go through clouds. These lenses are mostly used in eyeglasses to offer an all-in-one option as they block up to 100% of the UV when exposed to bright sunlight. They adapt to every environment and come back to clear eyeglasses in indoor environments.


Photochromic lenses have a lot of benefits and they can be cost-efficient as patients can buy one pair of eyeglasses instead of two. Patients who are looking for convenience will love having an all-in-one pair of glasses. With lenses of this kind, there is no need to carry two pairs of glasses everywhere at all times. The lenses also provide greater comfort because they reduce eye strain and glare in the sun. As they adapt to the level of light, they make it easy to achieve superior vision. Patients can also get photochromic technology with blue light blockers to enjoy complete protection from UV and blue light.


The technology used in the photochromic lenses is similar to the one used in car windshields. Windshields are designed to help drivers see in sunny conditions. Because windshields already filter UV light, the lenses might not become darker when driving. However,  new advancements in technology allow some photochromic lenses to darken even when receiving UV already filtered by the windshield.

This kind of lenses works via a chemical reaction. They are made with silver chloride. When silver chloride is exposed to ultraviolet light, the silver molecules gain an electron from the chloride to become silver metal. This gives the lens the ability to absorb visible light, turning darker in the process.

Photochromic lenses are made with similar chemicals used in the development of photographic films. Films are permanent while photochromic lenses are made with copper chloride. This is what helps the lenses to return to their normal state in the absence of UV light.