These lenses first appeared in 1964. They released the company Corning Glass Works, the developers who came up with the idea to apply the glass chemical compound of silver and copper. So lenses with a photochromic coating were created. They could change color in the sun. Buyers appreciated the novelty and began to use it with pleasure.
In the 80s of the last century optics manufacturers began to apply photochromic coatings on plastic lenses. In 1991 PPG Industries and Essilor International developed Transitions technology together. It allowed them to introduce the photochromic elements 0.1-0.15mm deep into the lens instead of just depositing them on the surface. Today most photochromic spectacle lenses are made with this technology.
How photochromic lenses work
While you are in the room, photochromic lenses remain transparent. You can freely read, watch TV or walk around indoors. But on the street such glasses darken and after 30-90 seconds they turn into sunglasses. This is possible thanks to the photochromic substances which are applied to the surface of the lenses. Checkout the huge varieties of contact lenses at https://www.contactlensesplus.com/
The darkness of the photochromes depends on the amount of sunlight that hits them. The photochromes applied to the lenses absorb ultraviolet waves and thus change their structure. Their molecules are rearranged so that the glasses change color. The more light hits the lenses – the darker they become.
When ultraviolet light stops the photochromic molecules revert back to their original position and the glasses become lighter.
Transition glasses work in the following way:
- Corrects vision. A photochromic coating can be applied to spectacle lenses with any number of diopters. Manufacturers use this to create glasses for people with myopia, astigmatism and presbyopia (age-related farsightedness).
- They protect the eyes from strain. Photochromes can darken in the sun. They do not let in bright light, so the sunlight stops blinding the eyes. This protects the person from visual stress and the appearance of little aesthetic wrinkles around the eyes.
- Protect against ultraviolet light. Glasses with photochromic lenses prevent ultraviolet waves from reaching the lens and retina. This prevents the development of cataracts, retinal dystrophies and other eye diseases.
Depending on the light, photochromes have different darkness (from 8 to 85%). This allows them to be worn at any time of the day. During the day photochromic lenses darken and protect the eyes from bright light, and in the evening they are lighter and do not interfere with a person’s vision.
Advantages of Transition glasses
Dark glasses for vision perform several functions at once, making them a substitute for several different means of correction.
Many people with myopia wear regular dioptric glasses indoors and replace them with sunglasses when outdoors. Or they wear contact lenses, and over them – sunglasses. You agree that this is uncomfortable. It is much better to buy one pair of glasses with photochromic lenses and wear them all the time.
People with age-related farsightedness are no exception. When they go out in the street, they experience discomfort from blinding their eyes to the sunlight. Wearing photochromes will help them get rid of this problem. For equally clear vision indoors and outdoors presbyopes should buy bifocal or progressive glasses with photochromic lenses.
Disadvantages of Transition glasses
Older models of photochromic lenses had many drawbacks. They did not darken well in the heat and did not want to change color in the car interior. Moreover, with time they “faded” and ceased to dim qualitatively.
Modern glasses have no such disadvantages. Thanks to the advanced manufacturing technologies their color does not depend practically on the air temperature. And due to the extended range of the perceived light waves they are easily darkened in the car.
Photochromic instead of sunglasses?
Modern photochromic lenses successfully replace sunglasses. What’s more, they outperform them in many ways. Photochromes not only provide 100% protection from harmful UV rays, but also provide a higher-quality visual perception. Due to the multilayer coating they remove glare and increase image contrast.
When the light conditions change the photochromes rapidly brighten. Thanks to this person does not need to constantly take off and put them back on.
Photochromes with an aspherical optical design have another advantage over sunglasses. They take away the visual aberrations that appear in any eye, even a healthy one. Glasses with these lenses provide a much better quality of vision than sunglasses.https://www.contactlensesplus.com/