Today’s topic is photochromic lenses that no longer darken. Below you will find an introductory guide to understand how a photochromic lens is built, how and why it reacts to direct sunlight and UV rays, which will help you understand why and when this situation occurs.
Photochromic lenses that don’t darken anymore, why?
Why don’t photochromic lenses darken anymore? As you can imagine, it is very simple the chemical treatment has run out. Technology advances continuously and allows us to count on numerous advantages in particular with more resistant chemical treatments and more performing lenses. As for photochromic lenses, the technological progress made in recent years has been enormous.
Despite the constant evolution in the construction of photochromatic lenses, their functionality is guaranteed for about 2 years or 2000 transitions from light to dark. Afterwards, wear and tear will take its course and make the lens not only slower in the transition but also increasingly less dark.
You can notice the color taken on by the lens when not in use; when a lens is discharged, it generally takes on a yellowish hue (depending on the category, it can be either transparent or smoked). If, upon removing the lens from the frame and exposing it to direct light, it reacts very slowly and with less intensity than a newly bought pair of glasses, it means it is time to change the lens, as it is no longer able to provide maximum protection from light and UV rays.
A second test would be to observe the reaction of the part of the lens that does not work when inserted in the frame; you will see that it will not only darken immediately, but it will reach a completely different color from that of the discharged lens.
At DEMON, we have all lens of eyeglasses available in our collection and out of production models to ensure the best customer service to our clients.
Tips for Increasing the Lifespan of Contact Lenses
There are some simple tips to follow to increase the life of the photochromic lens, they are small things that in the long run guarantee a longer duration of the photochromic treatment:
- Preservation: Store the lens in a cool and dry place inside its case (to prevent contact with light, even artificial when not in use).
- Lens Cleaning: Clean only with cold water lens and eyeglass at the end of every use. By cleaning sweat residues from the lens, it prevents a corrosive component from depositing and settling on the surface.
- Do not use in areas with high salinity, e.g. sea.
The salinity like sweat is very corrosive for the lens, in fact it can compromise the chemical treatment.
- Never leave the glasses at high temperatures, e.g. car dashboard, nor in direct sunlight (even if shielded by the glass of a window, e.g. shelf at home).
The usefulness of a photochromic lens in sports
Whatever outdoor sport is practiced, the first rule to be respected is to choose suitable filters that protect the eyes from light, possible accidental shocks, air, dust, insects and all projections that could come into contact with the eyes that drastically reduce perfect vision.
Photocromic lenses are true intelligent lenses.
For athletes, using a photochromic lens for outdoor activities means choosing a dynamic lens that adapts by darkening and lightening to all changes in light. For example, a cyclist or runner who uses a photochromic lens, the lens exposed to direct sunlight will start a chemical reaction that darkens the lens (it is important to know that the stronger the light and UV intensity is, the stronger the reaction will be, with benefits in reaction speed and greater darkness), in shadow areas where direct light is scarce or the reaction reverses back to its initial state.
In sports, photochromic lenses are therefore the most performing lens because they guarantee perfect vision in any light variation, thus allowing the athlete to focus solely on performance.
Protection of eyes from the sun and UV rays
The protection of eyes from the sun and UV of the photochromic lens is lower, equal or higher than the smoke sunglasses?
It is important to know that the protection offered by the photochromic lens from light and UV is the same as that guaranteed by the smoked sunglasses, however it should be noted that this degree of protection is established on a scale of values ranging from 0 to 4 called categories. Therefore, the photochromic lens will make a transition of 1, 2 or 3 categories of protection during the reaction. The maximum value reached by the transition therefore represents the maximum level of protection that can be achieved by the lens under optimal conditions.
In the DEMON collection there are several types of photochromic lenses, we summarize below with relative transitions:
- Photochromic 2-4: Transition from Category 2 to Category 4, specific lenses for alpinism, ski mountaineering and glacier.
- Photochromic Smoke 0-2: Transition from Category 0 (complete transparency) to Category 2 (equivalent to brown lens) can be used indoors and outdoors.
- DCHROM 1-3 Photochromatic: Transition from Category 1 (light smoke overlay) to Category 3 (darkness with mirrored lenses) for all outdoor sports even in very bright light conditions.
Construction of the Photocromatic Lens
The construction of a photochromic lens varies depending on the materials used: Glass or plastic material. In the construction of a photochromic glass lens, adding to the base mixture photchromic substances such as salts and micro-crystals of silver halide and or silver chloride.
In the sports world, the use of lenses in plastic material such as polycarbonate is preferred, because they are safer and more resistant in case of accidental impacts.
They prevent the creation of fragments that could cause very serious damage to the eye in case of very strong impacts.
To create the photochromic effect on plastic lenses, organic compounds such as oxazine or naftopirane or mixtures of indolino-spironafto-xazine are used; these light-sensitive substances change their chemical structure when exposed to UV radiation.
There are two methods for applying the treatment to the lens:
- By immersion: The lens is immersed in a tank of reactive liquid, then dried and treated with materials to ensure its protection and longevity.
- Application of photochromic film: a layer of photochromic film is inserted in the last layer, then treated with materials to guarantee its protection and durability.