How Do Photochromic Lenses Work?
Photochromic lenses are a marvel of modern eyewear technology providing a blend of functionality and convenience. These innovative lenses effortlessly "transition" from clear to tinted upon exposure to ultraviolet light, offering the dual benefits of standard eyeglasses and sunglasses in a single frame.
What Are Photochromic Lenses?
Photochromic is a generic term to define a lens with a characteristic of changing state from clear to sunglass dark when exposed to light. Over the years this option has been available in many different chemical, material, and color combinations; as well as offered by many different manufacturers with varying methods for application.
Photochromic lenses are lenses that stay transparent indoors, but darken when exposed to ultraviolet light from the sun. Essentially, they provide the benefits of glasses and sunglasses in a single frame.
The first photochromic lenses were patented in the 1960s and were made of glass. Plastic versions followed in the 1980s and ’90s, and are now the more popular choice among glasses wearers.
What Are Transitions Lenses?
Transitions is a brand of photochromic lenses. The word "transitions" is often used to refer to all photochromic lenses; like using "Kleenex" for tissue or "Coke" for soda,
Transitions lenses were created by PPG Industries (Pittsburgh Plate Glass Company). Transitions lenses use a technology called imbibing to place the photochromic dye just below the front surface of the lens. The advantage is that the lenses can be surfaced to a very thin center thickness without worry of the photochromic properties being changed. This technology also allows for uniform color in cases where the thickness between right and left lens varies.
What Are Neochromes Lenses?
Neochromes is a brand of photochromic lenses produced by IOT.
Neochromes by IOT offers a cutting-edge independent line of photochromic lenses. Like Transitions, these advanced lenses are designed to respond rapidly to light changes, Neochromes lenses darken swiftly outdoors and revert to clear visibility indoors in an impressively short amount of time. They offer comprehensive protection against harmful UVA and UVB rays, while also minimizing eye strain for enhanced comfort in any setting
Do Photochromic Lenses Have Other Names?
Photochromic lenses might also be called light-adaptive, photochromatic, or variable tint lenses, and of course Transitions or Neochromes.
How Do Photochromic Lenses Work?
The light-sensitive molecules inside photochromic lenses shift their structure when exposed to UV rays, allowing them to absorb more light and give the lenses a darkened appearance. Once the UV light goes away, the process reverses and the lenses become clear again.
Reaction to UV Light: In the presence of UV light, such as when you step outdoors into sunlight, the photochromic molecules undergo a chemical change. This change is triggered because these molecules are sensitive to UV rays.
Change in Structure: When exposed to UV light, the structure of the photochromic molecules changes, causing the lens to darken. This transformation happens because the altered structure of the molecules absorbs more visible light, effectively reducing the transmission of light through the lens and making them appear tinted or darker.
Reversibility: When you move away from UV light sources, such as going indoors, the absence of UV rays causes the photochromic molecules to revert to their original structure. This reversion causes the lenses to return to their clear state.
Speed and Degree of Change: The speed at which photochromic lenses change from clear to tinted and back again can vary based on the lens material and the ambient temperature. Generally, colder temperatures can make the lenses darken more deeply and may slow down the process of returning to a clear state.
Types of Lenses: Photochromic reactions can occur in both glass and plastic lenses, although the specific chemicals involved differ. In plastic lenses, organic photochromic molecules are used, whereas glass lenses typically use silver halide crystals to achieve the photochromic effect.
How Do Plastic Photochromic Lenses Work?
Plastic photochromic lenses have organic compounds within them that change their structure in the presence of UV light. These organic compounds are also known as photochromic dyes. When the dyes are exposed to UV rays, a chemical bond inside them breaks, and the dye transforms into a different molecule that absorbs more visible light.
How Do Glass Photochromic Lenses Work?
Glass photochromic lenses contain silver halide crystals (most commonly silver chloride) distributed inside the glass (sometimes referred to as en masse). When ultraviolet light hits these chemical compounds, the silver gains an electron and becomes elemental silver. The lenses appear darker as more and more silver molecules “appear” and absorb visible light.
In the absence of ultraviolet light, a second compound (typically copper chloride) embedded within the glass takes the transferred electron back from the silver metal reversing the process, making the lens transparent again.
A large disadvantage of en masse technology s the fact that with varying thicknesses the lenses would have a slight variance in color, this is apparent in plus lenses with darker centers and minus powers with lighter centers.
Glass photochromic lenses (PGX and PBX) aren’t as prevalent since glass is not a lens material commonly used anymore.
Do Photochromic Lenses Work in the Car?
Most photochromic lenses do not work in cars because they activate in response to ultraviolet (UV) light, which is generally blocked by a car's windshield. Therefore, while these lenses darken when exposed to direct sunlight, they will remain clear inside a vehicle where UV exposure is significantly reduced.
Are There Photochromic Lenses That Work in The Car?
Yes, there are photochromic lenses that can darken inside a car.
While they don't darken as much when not exposed to UV light, Transitions XTRActive lenses are designed to address the issue of photochromic lenses not darkening in cars. These lenses are capable of darkening in response to both visible and UV light, making them effective for use inside a car. They provide enhanced protection from bright light, both indoors and outdoors, making them suitable for people who are light-sensitive or frequently exposed to intense bright light.
DriveWear lenses are a sun lens that combine polarized filters with photochromic molecules that react to both visible and UV light. Unlike standard Transitions that only react to UV light, DriveWear lenses can adjust to daytime light conditions both inside and outside of the car. Because it is a sun lens, Drivewear is not recommended for indoor or nighttime use.
How Quickly Do Photochromic Lenses Work?
Photochromic lenses darken in 30–60 seconds on average when exposed to ultraviolet light. To clear, they take a bit longer: 2–3 minutes is normal.
How Does Temperature Affect Photochromic Lenses?
The rate at which photochromic lenses darken or clear up is impacted by temperature. When it’s colder, the lenses are apt to darken a bit more fully but take a longer time to clear up. When it’s warmer, they may not darken quite as much but will clear up more quickly, as the molecules within them are more reactive.
Do Photochromic Lenses Wear Out?
Eventually, your photochromic lenses will become less responsive to UV light and will take longer to shift between their two states. They may also take on a yellowish tint that signals their age. Most photochromic lenses will perform well for three years or more, however, so they’re still a long-term investment.
Advantages of Photochromic Lenses
So, are photochromic lenses worth it? Are they good for your eyes? In our opinion, the short answer is yes, but we’ve compiled their advantages below to help you decide.
They’re Convenient and Cost Effective
When you own photochromic glasses, you don’t need to buy separate frames for your prescription glasses and your sunglasses—you’ve got the best of both worlds in a single package.
This means you won’t have to carry sunglasses with you (and risk losing them or your other frames) on bright days. It also means that you won’t have to pay as much for the same perks, as photochromic lenses typically cost less than a pair of prescription sunglasses. In fact, you can get photochromic lenses in any of our frames for an additional $100.
They Provide Excellent UV Protection
Not only do photochromic lenses react to the presence of ultraviolet light—they shield your eyes from it! Our photochromic lenses block 100% of UVA and UVB rays, reducing your risk of developing UV-related cataracts and other problems.
They Filter Blue Light
Photochromic lenses filter more blue light from screens (and the sun) than lenses without photochromic properties. They can also reduce the effects of glare. (And, like all of our lenses, they come with scratch-resistant, anti-reflective, and superhydrophobic coatings.)
Disadvantages of Photochromic Lenses
Depending on your needs, photochromic lenses might also have some drawbacks.
They Can Take Some Time to Activate
If you’re extremely impatient, then the gradual shifting of photochromic lenses may not be for you. Their temperature sensitivity can also delay their transformations. Some people prefer the relatively instant swap to separate sunglasses.
Most Won’t Work While You’re Driving
Most modern car windshields have UV-blocking properties, so your photochromic lenses likely won’t darken all the way while you’re behind the wheel. The exception is DriveWear.
When Should You Recommend Photochromic Lenses?
Photochromic lenses are perfect for activities during which your environment might change. So, if you’re planning to grab lunch indoors and then go for a long bike ride, or hit up a museum after a walk in the park, their versatility can come in handy.
They’re also great for situations in which your hands will be occupied, preventing you from finding and putting on a separate pair of sunglasses. If you’re into kayaking, cycling, running, paddle boarding, or any other sport that involves the continuous use of your hands, then photochromic lenses can be a big help.
Some people choose to wear photochromic lenses pretty much constantly. Their light-responsive nature means that they’ll adapt to your surroundings, ensuring that you always feel prepared for a suddenly sunny day.