photochromic lenses that no longer darken

Today's theme is photochromic lenses that no longer darken. Below, you will find an introductory guide to understand how a photochromic lens is constructed, how and why it reacts to direct sunlight and UV rays, and what factors contribute to this situation..

Photochromic Lenses That No Longer Darken: Why?

Why do photochromic lenses no longer darken? As you might expect, the reason is quite simple: the chemical treatment has degraded. Technology continually advances, providing us with numerous benefits, particularly with more durable chemical treatments and increasingly high-performance lenses.

Regarding photochromic lenses, many technological advances have been made in recent years.

Despite these continuous improvements in the construction of photochromic lenses, their functionality is generally guaranteed for approximately 2 years or 2,000 light-to-dark transitions. After this period, wear and tear will inevitably occur, causing the lens to transition more slowly and gradually darken less and less.

You can observe this degradation from the color of the lens when it is not functioning properly. When a lens is discharged (whether transparent or smoked, depending on the category), it often takes on a yellowish tint. If you remove the lens from the frame and expose it to direct light, you will notice that it reacts very slowly and less intensely than a new pair of glasses, indicating that it’s time to replace the lens since it can no longer provide optimal protection from light and UV rays.

A second test involves checking the reaction of the part of the lens that isn’t working while it’s still in the frame. You will see that it not only darkens immediately but also achieves a completely different color compared to the unloaded lens.

At DEMON, we have all the eyeglass lenses available for both current and discontinued models to ensure the best assistance service for our customers.

 

 

Tips for Increasing the Life of Your Lenses

There are some simple tips you can follow to extend the life of your photochromic lenses. These small practices can significantly enhance the durability of the photochromic treatment over time:

Storage: Store the lenses in a cool, dry place inside their case to prevent exposure to light, even artificial light, when not in use.

Cleaning the Lenses: Clean your lenses and glasses only with cold water at the end of each use. Wiping away sweat residue prevents corrosive substances from settling on the surface.

Avoid High Salinity Areas: Do not use the lenses in areas with high salinity, such as the sea. Salinity, including sweat, is very corrosive to the lenses and can compromise the chemical treatment.

Avoid High Temperatures: Never leave the glasses in high-temperature environments, such as on a car dashboard or in direct sunlight, even if shielded by window glass (e.g., on a shelf at home).

 

The Usefulness of Photochromic Lenses in Sports

Any outdoor sport is practiced primarily in natural light. The rule to follow is to choose lenses that best protect the eyes from light, possible accidental impacts, air, dust, insects, and all projections that could come into contact with the eyes, which can drastically reduce optimal visibility.

Photochromic Lenses: Truly Intelligent Lenses

For athletes, using a photochromic lens for outdoor activities means choosing a dynamic lens that adapts by darkening and lightening in response to changes in light conditions.

Take, for example, a cyclist or runner using photochromic lenses. When exposed to direct sunlight, the lens undergoes a chemical reaction that causes it to darken. It’s important to note that the stronger the intensity of light and UV, the greater the reaction, leading to faster response times and increased darkness. In shaded areas, where direct light is limited, the lens reverses this reaction and returns to its initial state.

In sports, photochromic lenses are therefore the best-performing option because they ensure optimal visibility during every change in light, allowing the athlete to concentrate solely on performance.

Protection from the Sun

Are photochromic lenses inferior, equal to, or superior to smoked lenses in terms of protection from the sun and UV rays?

It's important to know that the level of protection against light and UV offered by photochromic lenses is comparable to that guaranteed by smoked sunglasses. However, it should be noted that this degree of protection is established on a scale that varies from 0 to 4, referred to as categories. The photochromic lens will transition between protection categories 1, 2, or 3 during use. The maximum value reached by the transition represents the highest level of protection that the lens can achieve under optimal conditions.

In the DEMON collection, there are different types of photochromic lenses, summarized below with their relevant transitions:

• Photochromic 2-4: Transition from category 2 to category 4; specific lenses for mountaineering, ski mountaineering, and glacier activities.
• Photochromic Smoke 0-2: Transition from category 0 (complete transparency) to category 2 (equivalent to a brown lens); can be used indoors and outdoors.
• Photochromic DCHROM 1-3: Transition from category 1 (light smoke haze) to category 3 (safety glass with mirrored lenses); suitable for all outdoor sports, even in very bright conditions.

Construction of Photochromic Lenses

The construction of a photochromic lens varies based on the materials used: glass or plastic.

In the construction of a photochromic glass lens, photochromic substances such as salts and micro-crystals of silver halide and/or silver chloride are added to the base mixture.

In sports, lenses made of plastic material, typically polycarbonate, are preferred because they are safer and more resistant in the event of accidental impacts. They help prevent the formation of fragments that could cause serious damage to the eye during strong impacts.

To create the photochromic effect on plastic lenses, organic compounds such as oxazines, naphthopyrans, or mixtures of indoline-spironaphtho-xazines are used. These light-sensitive substances change their chemical structure when exposed to UV radiation.

There are two methods to apply the treatment to the lens:

1. Immersion Method: The lens is immersed in a tank of reagent liquid, then dried and treated with materials to ensure long-lasting protection.

2. Application of Photochromic Film: A layer of photochromic film is inserted into the final layer of the lens, which is then treated with materials to ensure long-lasting protection.