Why Polarised Lenses?
What do Polarised lenses do?
So, your mate is raving about their new expensive Sunglasses with ‘Polarised Lenses’ and although you are very familiar with the term, you have zero clue what that actually means? Don’t panic, you are not alone (in fact your mate probably doesn’t know either!).
Put simply, polarised lenses only job is to prevent glare.
What is glare?
We all know that irritating moment where, even while wearing your sunglasses, you are forced to squint your eyes. Not a great position to be in if you are trying to navigate a rapid in your kayak, or racing downhill on your bike. Aside from inconvenience, and the obvious immediate danger that a lack of visibility can cause in these situations, it can also cause eye strain or eye fatigue (we promise that is a real thing!)
Now please bear with us through the boring science bit!
According to those science types, light bounces around in a million directions (like rockers in a mosh pit) but when it hits a reflective surface, which can include anything from a body of water or snow, to metal or glass, it becomes more organised or ‘polarised’ if you like. The light essentially groups into more uniformed directions, with a much higher intensity and glare is created when this light moves in a horizontal direction.
Your pupils are constantly reacting to light levels and having to deal with this ‘horizontal’ light can cause them to contract and expand while they try to adjust to both the intensity and angle. As you can imagine this is pretty stressful for your eyes and causes the eye strain/fatigue that we mentioned, which can then cause both headaches and migraines.
How do polarised lenses help?
Polarised lenses have teeny-tiny invisible lines on the lenses, that essentially work as a shutter to prevent horizontal lines of light reaching your eyes and causing the aforementioned havoc. Imagine your eye as a window, a vertical hanging blind would be the equivalent of a polarised lens. If a giant horizontal beam was shone through the window, you would only see the dots between the blinds rather than the entire line, which would cause the glare.
How can I tell if my lenses are polarised?
On the face of it, polarised lenses do not look any different from regular ones. They can come in any colour or mirrored finish, so how can you tell?
Now for a little party trick ……
- Hold your sunglasses out in front of you and look through them at a light screen of some kind. The screen should appear perfectly normal aside from being slightly darker depending on the lens colour.
- Now slowly rotate them 360 degrees, while still looking at the screen through the lens.
- As you turn a pair of sunglasses that are polarised, the screen will darken and then lighten again. On a non-polarised pair, the screen will just stay the same.
How are polarised lenses made?
The lines preventing the horizontal light waves getting through to your delicate peepers are usually either added as a film to the outside of the lens or embedded into the lens itself. The method used tends to be determined by the material of the Lens themselves, but both have the same effect of preventing glare.
Do Polarised lenses have UV400?
Now UV400 is a completely different kettle of fish. Our article Why do you need UV400 sunglasses will give you more detail, but in a nutshell, UV400 lenses prevent harmful UV radiation from reaching your eyes. Polarised lenses alone will give you no protection from these UV rays. If you want anti-glare and to protect your eyes from UVA and UVB (which you really should) then you need lenses that are both polarised AND UV400. Anything else will only do half the job.
On a side note though, ALL of our sunglasses have both UV400 and Polarised lenses!
When not to wear polarised lenses?
If you are in the habit of wearing your sunglasses at night (ridiculous!) then you need to be more cautious with polarised lenses. As mentioned in the ‘science bit’ earlier, polarised lenses work by limiting the vertical light that reaches your eyes. Simply put, that means less light gets through and so can be more dangerous in the dark than normal sunglasses, especially when driving! So, if for some reason you absolutely have to wear your polarised sunglasses in the dark, be careful and absolutely do not drive with them on!
In summary, all polarised lenses do is prevent glare, but that in itself is a very important task for a pair of sunglasses if you are wearing them around water or snow. You don’t buy Sunglasses to continue squinting through the lens. Their sole purpose is to make being outdoors more comfortable for you and keep your eyes protected, so that you can focus on the more important things! Make sure the sunglasses you buy give you that.