Burghley & Co Handbook
Photochromic Lenses Explained
Photochromic lenses are designed to stay clear indoors and darken outdoors when exposed to ultraviolet light. They can be incredibly convenient if you move between inside and outside throughout the day, but they are not always a perfect replacement for dedicated prescription sunglasses.
What are photochromic lenses?
Photochromic lenses are prescription lenses that automatically darken when exposed to ultraviolet light and become clearer again when the UV light is reduced. They are sometimes described as light-reactive lenses because they respond to changing light conditions.
The main appeal is convenience. Instead of constantly switching between your everyday glasses and prescription sunglasses, photochromic lenses allow one pair to adapt as you move from indoors to outdoors.
How do photochromic lenses work?
Photochromic lenses contain special light-reactive molecules within the lens material or coating. When UV light reaches the lens, those molecules change structure and the lens darkens. When UV exposure drops, the molecules return to their clearer state and the lens gradually fades back.
Modern photochromic lenses are much better than older generations. They usually react faster, become clearer indoors and offer more natural colour options than many people remember from older “reactive” lenses.
What are the benefits?
The biggest benefit is that you do not need to swap glasses every time light conditions change. This is useful when shopping, walking, travelling, commuting, gardening or moving between indoor and outdoor environments.
- Clear indoors and darker outdoors
- More convenient than carrying two pairs
- Useful for changing weather and variable light
- Available in prescription lenses
- Can reduce brightness and improve comfort outdoors
- Often include full UV protection
The honest limitations
Photochromic lenses are useful, but they are not perfect. They usually do not become quite as dark as a dedicated pair of sunglasses, and they may not darken as strongly behind a car windscreen because most modern windscreens block a large amount of UV light.
They also take time to change. They do not instantly turn dark the second you step outside, and they do not instantly clear the moment you walk indoors. The reaction is gradual.
Are photochromic lenses good for driving?
They can help in some driving situations, but this is where people need to be careful with expectations. Because photochromic lenses are mainly activated by UV light, they may not darken fully inside a car. A windscreen can reduce the UV reaching the lenses, which means the lenses may stay lighter than expected.
If you spend a lot of time driving in strong sunlight, dedicated prescription sunglasses are usually the better choice. If you only drive occasionally and mainly want everyday convenience, photochromic lenses may still be a very useful option.
Do they work on cloudy days?
Yes. UV light can still be present on cloudy days, so photochromic lenses can still react even when the sky does not look especially bright. They may not become as dark as they would in direct summer sunlight, but they can still offer extra comfort.
Do they work in winter?
Yes. In fact, photochromic lenses can sometimes become quite dark in cold bright conditions because temperature can affect how the lenses react. They can be especially helpful on bright winter days, although they still need time to fade back when you go indoors.
Are photochromic lenses the same as Transitions?
Transitions is a well-known brand of photochromic lens technology, but not every photochromic lens is a Transitions lens. Photochromic describes the type of lens technology. Transitions is one branded version of that technology.
There are several types and generations of photochromic lenses, and performance can vary between them.
Photochromic lenses vs prescription sunglasses
Photochromic lenses and prescription sunglasses solve slightly different problems. Photochromic lenses are about everyday convenience. Prescription sunglasses are about dedicated sun protection and a consistent sunglass experience.
| Option | Best for | Limitations |
|---|---|---|
| Photochromic lenses | Everyday convenience, changing light, one-pair wear | May not go as dark as sunglasses and may not darken fully in cars |
| Prescription sunglasses | Driving, holidays, beach, bright sun, glare control | You need to carry a second pair |
For more detail, read our prescription sunglasses guide.
Can photochromic lenses be polarised?
Some specialist lenses combine photochromic and polarised technology, but standard photochromic lenses are not automatically polarised. If glare from roads, water or wet surfaces is your main problem, polarised prescription sunglasses may be more effective.
You can learn more in our guide to polarised lenses.
Who are photochromic lenses best for?
Photochromic lenses are best for people who want convenience and spend their day moving between indoor and outdoor environments. They suit everyday wear, errands, walking, commuting and general lifestyle use.
They are less ideal for someone who wants very dark sunglasses, spends long periods driving in bright sunlight or wants the most effective glare reduction around water and roads.
Scott’s advice
I like photochromic lenses for people who want one practical everyday pair and do not want the hassle of constantly changing glasses. They are especially useful if you are in and out of buildings during the day.
However, I would not describe them as a full replacement for prescription sunglasses. If you drive a lot, go abroad regularly or prefer a proper sunglass look, a dedicated pair of prescription sunglasses will usually do the job better.
The honest answer is that many people benefit from both: photochromic lenses for everyday convenience, and prescription sunglasses for stronger sun, driving and holidays.
Related guides
For more help, read our guides to prescription sunglasses, polarised lenses, choosing prescription lenses, lens coatings and choosing glasses frames.
FAQs
Do photochromic lenses work through a car windscreen?
They may react slightly, but they often do not darken fully inside a car because many windscreens block a large amount of UV light. Dedicated prescription sunglasses are usually better for regular driving in bright sun.
How dark do photochromic lenses get?
This depends on the lens type, UV level, temperature and conditions. They usually darken enough for everyday outdoor comfort, but they may not become as dark as dedicated sunglasses.
How long do photochromic lenses take to change?
They begin changing shortly after UV exposure, but the process is gradual. They normally darken faster than they clear, and clearing indoors can take a little longer.
Do photochromic lenses protect against UV?
Most modern photochromic lenses include full UV protection, but this should always be checked when choosing your lenses.
Are photochromic lenses worth it?
They are worth it if you value convenience and move between indoors and outdoors often. They may be less worthwhile if you mainly want very dark sunglasses or strong glare reduction while driving.
Do photochromic lenses work in winter?
Yes. They can still react in winter because UV light is still present. In cold bright conditions, they may sometimes darken strongly.
Are photochromic lenses the same as Transitions lenses?
No. Photochromic is the type of technology. Transitions is a well-known brand of photochromic lenses.
Can photochromic lenses be made with my prescription?
Yes. Photochromic lenses can usually be made in many prescription types, including single vision and varifocal lenses, depending on your prescription and frame choice.
Need help?
Unsure what to choose?
If you are not sure about your prescription, frame size or lens choice, ask before you order.