Let’s talk about photochromic lenses

Photochromic lenses are lenses that can automatically adapt to changes in ambient light. This means that they can darken or lighten in response to changing light conditions. When exposed to UV light, photochromic lenses darken to reduce light intensity. On the other hand, in low light conditions, such as shaded environments, the lenses lighten to provide clear and comfortable vision.

How exactly do they work?

Photochromic lenses contain photosensitive chemicals, usually composed of organic compounds such as silver halides, that react to ultraviolet (UV) radiation in sunlight. When these substances are exposed to UV radiation, a photochemical reaction occurs that leads to a change in the molecular structure of the photosensitive compounds.

Since it is a chemical reaction and not an explosion, photochromic lenses do not adapt instantly to light. In fact, they take about 10 seconds to go from clear to dark, but take several minutes to return from dark to completely clear. In addition, temperature affects the speed of adaptation; in particular, cold slows down the reaction.

Visible light does not include UV

It is also important to know that visible light, the light perceived by our eyes, is not the same type of light to which photochromic lenses react. Therefore, under certain conditions, photochromic lenses do not respond perfectly to the needs of our eyes.

For example, clouds block visible light more than UV rays, so you may end up with photochromic lenses activated even in conditions that our eyes perceive as dark.

Similarly, in the car, since the windscreen blocks 99% of UV rays, photochromic lenses do not activate.

What are the advantages of photochromic lenses in sporting activities?

Despite some limitations, such as the slow reaction to light, photochromic lenses cover a wide range of conditions with a single lens, allowing the user not to change lenses and to have only one pair of goggles or one pair of ski goggles for all conditions.

Are there any cons?

Photochromatic lenses have no significant disadvantages compared to normal static lenses; on the contrary, they represent a great step forward, especially for sports use.

However, this type of lens has a decay factor: the organic compounds inside become less sensitive to changes in light after four or five years of use, depending on the type.

Are these the right lenses for you?

It depends! Not everyone has the same needs. If you are looking for a dynamic lens that can adapt well to slow changes in light, then a photochromic lens is for you. If you also want something that blocks glare, look for photochromic and polarised lenses.

On the other hand, if you don’t mind having several pairs of sunglasses or if you only use them in relatively sunny conditions, it might not be worth spending extra money on a photochromic lens.