The Ultimate Guide on How Photochromic Lenses Work

The word photochromic is made up of two words that are photo and chromatic.

• Photo refers to the light 
• Chromic refers to the color

It is noted that photochromic materials are the type of materials that undergoes the changes that are reversible in nature (especially the color) when they are exposed to a certain amount of ultraviolet radiation that can cause the changes to occur. A very good example of such an application is the polycarbonate photochromic sheet and film, which can change its color on exposure to ultraviolet radiation. This change in the color is, most of the time result of the reaction that occurs in photochromic compounds in these materials, as a certain amount of exposure to ultraviolet radiations initiates such changes in the molecular structure of the photochromic compound that are reversible in nature, this is the reaction that can lead to the darkening of the lenses. However, the intensity of the tint and the uniformity are dependent on the chemical composition of these molecules that are there on the lenses.

What is a Photochromic Lens?

A photochromic lens is a type of lens that remains clear indoors that is in the absence of ultraviolet radiation. However, it changes color and darkens when it is exposed to a specific amount of UV light. Most of the time, it generally takes about 30 seconds for the lens to get fully tinted but around 2 to 5 minutes to get back to its original color. These photochromic lenses could be made up of various different materials, however, the most common type of materials that are used are glass and polycarbonate sheets that are plastic. Nowadays, we get to see that polycarbonate sheets are used very commonly as photochromic lens material.

However, if one wants to shop high-quality photochromic lenses, then there are various other qualities that one must look for. This includes the property of being shatterproof and various other desirable features as well. The first person who invented this lens was Roger Araujo; however, there is still research going on in order to make it even better by bringing innovation as the companies and manufacturers keep on trying to modify these lenses according to the demand of their clients. This is the reason that we nowadays get to see photochromic lenses exhibiting the features of the organic molecules as opposed to the silver compounds. 

How do they Work?

Photochromic materials are seen to darken when exposed to a specific amount of Ultraviolet light. However, in the absence of ultraviolet light, the color reverses back to what it was originally, making it become clear, that this is the result of the changes that occur at the molecular level within a photochromic material. 

How does a glass photochromic lens work?

The first ever photochromic lens was made up of glass. However, the main photochromic element in these lenses was mostly silver compounds that were in the form of substances like silver chloride or silver halide. These compounds were mainly embedded in the glass substrate that could vary in terms of size; however, the most common size was about 5 nanometers. Here the reason for the tinting is the reaction at the molecular level.

How polycarbonate photochromic Lenses work

With the commercialization of plastic photochromic lenses, we get to see that there are a number of manufacturers that go for the option of polycarbonate sheets to be used as an alternative that is better in option. However, by adopting polycarbonate materials, one can manufacture a huge variety of photochromic lenses that vary in terms of design as well as shape. But the principle at which the photochromic lens works is quite different from that of glass. The photochromic lens is dependent on carbon-based compounds. Until now, we see a significant improvement in the industry as it is producing fast reacting and more effective photochromic surfaces. This could be seen by the example that in the early times, photochromic lens manufacturers were using pyrido benzoxazines, which was an organic dye. Nowadays, we see the use of naphthopyrones, with others opting for indenonaphthopyrans more commonly. 

Benefits of These Photochromic Lenses

Reducing the Unnecessary expenses 

When we buy a lens that can be used in both the situations, whether it is indoor or outdoor, it turns out to be a cost-effective option in the long run, for instance, a photochromic lens that can automatically be adjusted depending on the intensity of the ultraviolet radiations that are there in the surrounding. Thus, it can help save the cost of two separate glasses and sunglasses. 

Guaranteed UV protection

These lenses provide ultimate protection against harmful ultraviolet radiation without straining the natural defense mechanism of the eye to prevent harmful ultraviolet radiation.

Convenient to Use

One does not have to switch from glasses to sunglasses and vice versa in order to protect your eyes every time you go out or move in. Thus it is considered a more convenient option.