Chloe Zhang
Plastic photosensitive lenses, also known as photochromic lenses, are eyeglass lenses that automatically darken when exposed to sunlight and become clear again when removed from the light source. They are made of carbon-based compounds that change their structure in the presence of UV light. The lenses appear darker as these compounds absorb more visible light. Photochromic lenses are a convenient alternative to carrying multiple glasses frames, as they can be used both indoors and outdoors. The most popular brand of photochromic lenses in the US is Transitions Optical, and their lenses are often referred to as transition lenses.
| Characteristics | Values |
|---|---|
| What are they? | Photochromic lenses, also known as transition lenses, are eyeglass lenses that turn dark in sunlight and become clear again when indoors. |
| How do they work? | Plastic photochromic lenses have carbon-based compounds (photochromic dyes) within them that change their structure in the presence of UV light. |
| How do they compare to glass photochromic lenses? | Plastic photochromic lenses are more common than glass ones and react to light more quickly. Glass photochromic lenses are heavier and less impact-resistant but offer superior scratch resistance. |
| Brands | Transitions Optical is the most popular brand of photochromic lenses in the United States. Other brands include Hoya Vision Care, Vision-Ease Lens, and Corning. |
| Types | Transitions Gen 8, Transitions XTRActive, Transitions Vantage, SunSensors, PhotoGray, PhotoBrown, Thin & Dark |
| Uses | Photochromic lenses are useful for driving, sports, outdoor activities, and reducing glare from electronic devices. They can also be used as contact lenses. |
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What You'll Learn
Photochromic lenses are made of plastic or glass
Photochromic lenses are optical lenses that darken when exposed to light of a high frequency, usually ultraviolet (UV) radiation. They are available in both plastic and glass varieties.
The first photochromic lenses were made of glass and were patented in the 1960s. They contain minute amounts of silver halide crystals, usually in the form of silver chloride. When UV light hits these chemical compounds, the silver gains an electron and becomes elemental silver. As more silver molecules form, the lenses darken. Glass lenses are scratch-resistant but heavier and more prone to shattering than plastic lenses. They are also less prevalent in the eyewear world today.
Plastic photochromic lenses were introduced in the 1980s and are now the more popular choice. They contain carbon-based compounds, also known as photochromic dyes, which change their structure in the presence of UV light. When exposed to UV rays, a chemical bond inside them breaks, and they transform into a different molecule that absorbs more visible light, resulting in darker lenses. Plastic lenses are typically embedded with the material into the surface layer of the plastic in a uniform thickness of up to 150 μm.
Polycarbonate is a commonly used plastic for photochromic lenses. Plastic lenses are lighter and more impact-resistant than glass lenses, but they may not be as scratch-resistant. They also tend to darken more in cold weather and take longer to return to their clear state when they are colder.
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$17.99 $19.99
Plastic photochromic lenses use carbon-based compounds
Plastic photochromic lenses, also known as transition lenses, use carbon-based compounds within them that change their structure in the presence of UV light. These organic compounds are also known as photochromic dyes, with chemical names like pyridobenzoxazines and indenonaphthopyrans. When exposed to UV rays, a chemical bond inside them breaks, and they transform into different molecules that absorb more visible light. This increased light absorption causes the lenses to darken, providing the benefits of both glasses and sunglasses in a single frame.
The process of darkening in plastic photochromic lenses occurs more quickly than in glass photochromic lenses. Glass lenses contain silver halide crystals, typically silver chloride, which darken when exposed to UV light as the silver gains an electron and becomes elemental silver. Plastic lenses, on the other hand, use carbon-based compounds that react rapidly to UV light, allowing them to darken within about a minute of exposure.
The first photochromic lenses were introduced in the 1960s and were made of glass. Plastic photochromic lenses were later developed in the 1980s and 1990s and have since become the more popular choice among glasses wearers. Plastic lenses offer advantages such as being lighter and more impact-resistant than glass lenses, making them a convenient and trendy option.
The popularity of plastic photochromic lenses has led to ongoing research to enhance their performance further. Scientists are working with photochromic dyes to increase the reactivity of the lenses, aiming for quicker darkening and clearing times. Additionally, advancements are being made in lens design, such as Transitions Optical's Gen 8 lenses, which offer faster light adaptation and improved clarity.
The versatility of plastic photochromic lenses is demonstrated by their availability in various designs, including gray and brown tints. They are also suitable for contact lenses, with brands like Acuvue Oasys with Transitions offering light-intelligent contact lenses that darken automatically in response to UV and High Energy Visible (HEV) light. The adaptability of plastic photochromic lenses makes them a preferred choice for many individuals seeking both functionality and style.
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Glass photochromic lenses use silver halide crystals
Glass photochromic lenses, also known as self-darkening eyeglasses, use minute amounts of silver halide crystals, most commonly silver chloride, distributed inside them. When ultraviolet light hits these chemical compounds, the silver gains an electron and becomes elemental silver—the silver metal with which you’re probably familiar from jewellery or cutlery. The lenses appear darker as more and more silver molecules “appear” and absorb visible light.
The process is similar to the development of photographic film: exposure to light causes the image to darken and develop. However, unlike photos, glass photochromic lenses are able to revert to their original clear appearance. This is because, in the absence of ultraviolet light, a second compound (typically copper chloride) that’s also embedded within the glass takes the transferred electron back from the silver metal. The process reverses, and the lenses become transparent once more.
The first photochromic lenses were made of glass and patented in the 1960s. Plastic versions followed in the 1980s and ’90s and are now the more popular choice among glasses wearers. Plastic photochromic lenses have carbon-based compounds within them that change their structure in the presence of UV light. These organic compounds are also known as photochromic dyes and react to light more quickly than the chemical compounds in glass photochromic lenses.
Photochromic lenses are a blend of functionality and convenience, providing the benefits of glasses and sunglasses in a single frame. They are also more cost-effective than buying separate pairs of prescription glasses and sunglasses.
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Transitions Optical is a popular brand of photochromic lenses
Plastic photochromic lenses, also known as photochromatic lenses, are lenses that automatically darken when exposed to UV light. This is achieved through the use of carbon-based compounds within the lenses that change their structure in the presence of UV light. These compounds, also known as photochromic dyes, have long names like pyridobenzoxazines and indenonaphthopyrans. When exposed to UV rays, a chemical bond inside them breaks, and they transform into a molecule that absorbs more visible light, resulting in darker lenses.
- Transitions Gen 8: These lenses, introduced in July 2019, are the fastest light-adaptive lenses offered by the company. They get darker and become clear again more quickly than other lenses, taking 30% less time to activate and fade back.
- Transitions XTRActive: These lenses are designed for individuals who are light-sensitive indoors and prefer darker lenses when outdoors or driving. They have a slight indoor tint to reduce glare and harsh lighting from digital devices and fluorescent lights.
- Transitions Vantage: Vantage lenses have a minimal indoor tint and a stronger polarization effect for outdoor darkening, providing better glare control in bright and reflective conditions. The polarization adjusts constantly to match the level of reflective glare, resulting in a "high-definition visual experience."
- Transitions Drivewear: These polarized adaptive lenses are specifically designed for driving, providing improved visibility behind the wheel.
The popularity of the Transitions Optical brand has led to the common use of the term “transition lenses” or "transitions" to refer to photochromic lenses in general. However, it is important to note that there are other brands of photochromic lenses available as well.
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Photochromic contact lenses are also available
Photochromic contact lenses, such as Acuvue Oasys with Transitions, are now available. These lenses are a first-of-its-kind innovation, built with Transitions Light Intelligent Technology to help reduce exposure to bright light both indoors and outdoors. They are made of plastic and contain carbon-based compounds that change their structure in the presence of UV light. This technology allows the lenses to darken automatically when exposed to UV and High Energy Visible (HEV) light, reducing disruption to vision due to bright light by up to 32%clear state within 90 seconds when removed from the light source.
Acuvue Oasys with Transitions contact lenses are available by prescription only for vision correction. An eye care professional will determine whether contact lenses are suitable for the patient. These lenses are not a substitute for sunglasses, and they should be replaced every two weeks. They feature scratch-resistant, anti-reflective, and superhydrophobic treatments and block 100% of UVA and UVB rays.
Other contact lenses from brands such as Biotrue and Clariti also block UV radiation while remaining clear in all light conditions. Throughout the day, these lenses change colour between clear and a deep, dark purple-brown. In bright, direct sunlight, the darkening effect is most noticeable, and they may give the wearer a distinct alien-like appearance.
Photochromic contact lenses are a convenient option for those who don't want to carry multiple glasses frames or switch between glasses and sunglasses. They can also help individuals who experience photophobia, which is associated with conditions such as migraines and dry eye.
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Frequently asked questions
Plastic photochromic lenses, also known as transition lenses, are eyeglass lenses that automatically turn dark in sunlight and become clear again when indoors.
Plastic photochromic lenses have carbon-based compounds within them that change their structure in the presence of UV light. These organic compounds are also known as photochromic dyes. When exposed to UV rays, a chemical bond inside them breaks, and the dye turns into a different molecule that absorbs more visible light.
Plastic photochromic lenses are a convenient two-in-one solution, eliminating the need to carry multiple glasses frames. They are also more impact-resistant than glass photochromic lenses and less likely to break if dropped.
Popular brands of plastic photochromic lenses include Transitions Optical, Corning, Hoya Vision Care, and Vision-Ease Lens. Transitions Optical is the most popular brand in the United States and offers a range of lenses, including Gen 8, XTRActive, and Vantage.
One potential drawback of plastic photochromic lenses is that they may not be as scratch-resistant as glass lenses. Additionally, they may not be as clear indoors compared to other photochromic lenses.
