Photochromic Glasses: How They Work Plus Pros and Cons

Ever wished you didn’t have to carry around two pairs of glasses for those sunny days when you’re moving between indoors and out? That extra pair often seems to weigh heavy in your purse or pocket and it’s not always convenient to change your glasses on the fly.

You’ll be happy to know that we’ve got a solution for you: photochromic lenses.

Let’s learn what photochromic lenses are and how they work. We’ll highlight some pros and cons you need to know and then share where to get your handy pair of photochromic specs. You’ll never look back — or find yourself squinting in bright sunlight — again.

What Are Photochromic Lenses?

Photochromic lenses change color depending on the level of light in your surroundings, protecting your eyes no matter where you are.

When you’re indoors or in other low-light conditions, photochromic lenses are completely transparent and look like normal glasses. But the moment you move into bright light, the photochromic magic kicks in and their tint darkens.

How much they darken depends on the amount of UV light. For example, if it’s an overcast day or you’re in the shade, they’ll only darken slightly (compare this to sunglasses, which may be too dark for those kinds of conditions). On the other hand, if you’re standing in bright sunlight, photochromic lenses will turn a much darker shade.

Photochromic lenses are also known as transition lenses, variable tint lenses, photochromatic lenses, light-responsive lenses, or light-adaptive lenses.

Interesting side note: The term “photochromic” comes from the Greek words “photo” and “chroma,” which mean “light” and “color.”

How Do Photochromic Lenses Work?

The Jessie

The first photochromic lenses were patented in the 1960s and were made of glass. Glass transition lenses have a type of silver halide crystal — usually silver chloride — embedded in the lens. When they’re exposed to ultraviolet light, the silver halide gains an electron, becoming silver metal. Silver absorbs more of the light hitting it and the lenses darken as a result, usually turning brown (depending on the lens brand).

Then when the amount of UV light lessens, another compound — often copper chloride — takes the electron back and you soon have clear lenses again.

Glass lenses have mostly been replaced with plastic ones now and the technology works slightly differently. Plastic photochromic lenses contain carbon-based photochromic dyes. When UV rays hit this type of lens, the photochromic molecules move and change form — and you quickly find yourself wearing photochromic sunglasses.

When the light dims again, the molecules return to their original form, producing clear lenses once more.

The darkening process usually happens within about a minute. However, it can take a little longer — up to three minutes — for the lenses to turn transparent again.

Pros and Cons of Photochromic Eyeglasses

While there are many benefits to wearing photochromic lenses, they also have a few drawbacks. Let’s cover both sides of that equation so you can decide whether this type of lens is for you.

The Pros

There are so many reasons to wear photochromic glasses. Just for starters:


With photochromic lenses, you get two pairs of glasses in one. No more carrying around that extra pair of sunglasses and potentially misplacing them (this goes double for kids). They’re also great for activities like cycling or paddleboarding, where you don’t have a spare hand to change your glasses on the move.

Great Value

Buying one pair of photochromic prescription glasses is cheaper than buying a normal pair plus a pair of prescription sunglasses. Photochromic lenses usually last for at least three years before they start to lose their ability to transition between shades — by which time, you’ll probably need a new prescription anyway.

UV Protection

Photochromic lenses protect your eyes from harmful UVA and UVB rays. This reduces your risk of getting wrinkles or developing sun-related eye conditions like corneal sunburn or cataracts.

Better Sleep

Transition lenses filter out more blue light than clear lenses. As blue light can interfere with your sleep patterns, this is handy if you’re often online at night.

The Cons

It’s a good idea to be aware of these potential issues too before you make your decision:

Delayed Reaction

The lenses do take some time to darken and even more to lighten, and how fast they adjust also depends on temperature. This can mean you come in from outside and your glasses are still dark as they adjust to the light. So if you need a faster change, you may be better off with a separate pair of sunglasses.

Best for Short Time Frames

Photochromic lenses work well if you often head outside for short periods. If you spend long hours outside, you might prefer prescription sunglasses. These usually have darker lenses, offering your eyes more protection. Plus — although photochromic glasses do help to reduce some glare — polarized lenses are even better at cutting out the reflection from surfaces like water and snow.

Not Ideal for Driving

Photochromic lenses are activated by UV light — and most car windscreens these days block those UV rays. So your transition glasses might not turn dark enough to protect your eyes while you’re on the road.

Where to Get Your Photochromic Glasses

Woman holding a pair of photochromic glasses

Pair Eyewear offers a wide range of customizable glasses, including photochromic lenses. Simply add on transition lenses when you order your normal prescription glasses.

Bear in mind that although you can get transition lenses for any frame, you’ll get more coverage and sun protection from bigger frames than smaller ones.

Photochromic functionality can be added to any prescription from single vision lenses to bifocals or even readers — which is helpful if you’re developing presbyopia and want to be able to read outside.

Pair glasses are built to last with hard-wearing cellulose acetate frames and polycarbonate lenses. All our lenses — whether they’re photochromic or not — take eye care to the next level, coming standard with anti-reflective and scratch-resistant coatings.

Style Your Pair Eyewear

At Pair, we believe glasses can be both functional and stylish. So we make it easy for you to style any pair of Base Frames with a magnetic Top Frame (or two) to match your personality or the occasion. Go ahead and choose your Top Frame from our gorgeous Collections, Limited Editions, or Collab ranges.

We’ve also solved the problem of photochromic lenses not being suitable for driving. Simply snap on one of our magnetic Sun Tops to your regular prescription glasses to create instant sunglasses with style. And if the light conditions change again, it takes just a second to remove the Sun Top and return your glasses to normal again. Just like our sunglasses, Sun Tops are also 100% UVA and UVB resistant and they come in a range of colors, including mirrored lenses.

If you’d like more information about any aspect of Pair’s range of eyewear, try our FAQ pages first for a quick answer. You’re also welcome to contact us directly at [email protected].

Protect Your Eyes on the Move With Photochromic Lenses

The Galaxy Sun Top

If you’re someone who often moves from indoors to out and back again, photochromic lenses can save you the hassle of constantly having to change your glasses. They also protect your eyes from UV light and offer better value for money than buying two pairs of prescription glasses.

There are circumstances when normal sunglasses might work better for you, but for most people, photochromic lenses make life a lot easier.

Get your photochromic prescription glasses from Pair Eyewear today and take your style up a notch at the same time. Our unique Base Frame and Top Frame combo makes it easy to change your look in seconds — and protect your eyes while driving. Order a Pair today and see the world through new eyes, day and night.