Cold and Warm Temperatures: Differences in the Optical Properties of Photochromic Lenses

Posted by Mitch Gantman on

Cold and Warm Temperatures: Differences in the Optical Properties of Photochromic Lenses

Many people who live in colder climates are often unaware that they should wear sunglasses with photochromic lenses to protect their eyes from the glare on snow or frosty surfaces. This is because photochromics change color depending on the temperature outside, which can be helpful when it gets dark early during the winter months.


What are Photochromes?

Photochromes are sunglasses that change color depending on the temperature outside. The higher the ambient (or surrounding) temperature, the darker they are to protect our eyes from UV rays and bright light indoors or out. ; the colder it is, the lighter they become to allow more light in.

Photochromic lenses are designed for variable environments where you may be driving into a dark tunnel and then out again outdoors, descending from an air-conditioned office building into bright sunlight on street level, or sunning yourself outside of a cold swimming pool. Having photochromic lenses in your eyewear makes adapting to changing light conditions easy.

When wearing photochromes indoors or out, you'll notice that they will darken when it's cold outside, and the intensity of UV rays is high; they may also get lighter while driving into a tunnel with low-level lighting.


Photochromic Lenses

A photochromic lens is made of plastic that reacts to ultraviolet light by changing color in response. The reaction happens when the sun's rays hit the lenses, which causes them to darken or change from clear to colored depending on what type of material they are and how much UV they receive.

The main difference in the optical properties of photochromic lenses is that they are less efficient at blocking UV rays and visible light when it is cold. This is because they require higher temperatures to activate the color-changing chemical reaction. When you wear a pair of glasses, this can cause vision problems such as snow blindness or blue haze. 

Photochromic lenses have two reactions: One that is activated by warmer temperatures and one that's triggered by cold. Cold temperatures have a shorter range of light sensitivity than the warm temperature, which is just below 27 degrees Fahrenheit or less than 0° Celsius. 


Optical Properties of Photochromic Lenses for Warm Temperatures

In the summertime, when you're outside all day long and then come inside at night to finish up your homework or watch a movie, it's important that the lenses lighten. Otherwise, these activities will begin to strain your eyes as they adjust from bright sunlight to darker. To get the lenses to darken enough, you might need a darker lens color for wintertime and then switch back to a lighter one when the weather starts warming up again. 

When you're wearing photochromic lenses in the summertime, they should darken to protect your eyes from UV light exposure.


Optical Properties of Photochromic Lenses for Cold Temperatures

When you're wearing photochromic lenses in the wintertime, they should lighten to allow more UV light through so that your eyes can tell whether it's day or night outside. An excellent way to test this is by walking into a mall and looking at one side of the building, which will be lit by sunlight, and then turning around to look at the other side of the building. 

However, suppose you're outside in a snowstorm or otherwise heavily shaded area when wearing photochromic lenses that are designed for cold temperatures. In that case, they should darken more than usual because UV light is less prevalent. In this case, you should be careful to wear shades when you're outside.

In the winter, your photochromics should turn light to allow you to see better in bright sunlight. This is because when it's cold outside, and there are no clouds or fog, glare from the sun becomes a problem. In addition, if you use lenses that don't provide protection from UV rays, you're more at risk for snow blindness.

Transitions 8 vs Xtractive

Transitions 8 vs Xtractive: both are one of the best transition lenses to have. Transition lenses are used by people with myopia, hyperopia, or presbyopia. Transition lenses are suitable for driving and close work because they provide the best contrast of any lens type available to those with these conditions. And when you go outside from indoors, your eyes will feel more refreshed than if they had been wearing traditional single-vision lenses thanks to a UV blocker built into the material.

How to Tell if a Lens is a Cold or Warm Photochrome?

If a lens has the following properties, then it is designed for cold temperatures:

- UV protection and high contrast in low light conditions;

- It will darken quickly in shaded areas or during snowstorms.

A material that does not have these properties is most likely made for warm environments. The difference between how they react in light is what makes them ideal for cold or warm climates.

In these photochromic lenses, UV protection and contrast work together to provide a clearer sight in low-light conditions, which are often found at higher altitudes. What's more, they will darken quickly when shaded by clouds or snowstorms, meaning that bright sunlight isn't as much of a burden.


Benefits of Photochromic Lens

Here are a few benefits of photochromic lenses:

- They're a great option for people who want to have sunglasses that are lighter in the summer and darker in the winter.

- The technology allows you to adjust your vision depending on what's happening outside, so if it's sunny out or there is snow falling outside (both causes light levels to increase), you can use your photochromic lenses to make the outside world more visible.

- Photochromics are an excellent choice for people who have sensitive eyes, headaches, or other symptoms related to glare and UV light exposure because they're gentle on your eyes.

The benefits of wearing photochromic lenses depend largely on what's happening in your area. For example, if you live somewhere that gets a lot of snow, you'll be glad to know your lenses will darken when there's more sunlight outside, making it easier to see and reducing the glare on the road.

If you live in an area with lots of sunshine all year long, like Southern California or Florida, your lenses will ideally switch from dark to clear when you go inside.

But what about if it's a cloudy day? You'll be happy to know that photochromics can still adjust for the light level indoors or outdoors and even let some natural light in a while absorbing UV rays—that way, your eyes are protected no matter what the weather. 


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