Polarized Sunglasses, What Exactly Are They?

wearing polarized sunglasses, Zenni optical

You’ve probably seen drugstore sunglasses labeled “polarized.” Maybe you looked at those next to sunglasses that weren’t polarized, and wondered what the difference was. Or maybe your eye dr. recommended getting polarized lenses, but you weren’t sure how they worked and what benefit they offered.

Well, we’re going to tell you! Very simply, here’s what polarized lenses do: they reduce glare by blocking horizontal light rays.

Why horizontal? Here’s a little background on how polarization works: light comes from the sun in all directions, and it is reflected in every direction, too. When it reflects from light-colored horizontal surfaces – such as a white sidewalk, a white-sand beach, snow, or sunlight reflecting on water – it is said to be polarized horizontally. Light that is polarized horizontally is responsible for most of the glare that interferes with our vision.

How do polarized lenses work? To understand this, it’s useful to think of window blinds. Let’s start with Venetian blinds, which are horizontal. When Venetian blinds are open, light comes into the room in horizontal stripes, depending on the angle of the sun and the angle the blinds are open.

Polarized lenses are more like vertical blinds. When vertical blinds are open at a certain angle, light comes into the room in vertical stripes. Since horizontally reflected light is responsible for most of the glare we see, the polarized tint is placed on the sunglass lens in vertically angled strips. These vertical strips of tint allow vertically reflected light into the eye but block horizontally reflected light – greatly reducing horizontally polarized glare.

Most polarized lenses are sunglasses. Polarized sunglasses are especially popular with boaters, since water is a very reflective surface on a sunny day. Polarized sunglasses are also great for other outdoor activities, such as golfing and tennis, since they can help to sharpen the focus on the ball. They can also be good for driving, since polarized lenses reduce the glare that reflects from the shiny hood of a car, or the glare from the surface of the road on a hot, sunny day.

However, in some situations there can be drawbacks to polarized lenses. They can be problematic for skiing, since blocking the reflected glare off an icy patch might prevent the skier from noticing and steering away from a potential hazard.

In addition, it can sometimes be difficult to read liquid crystal display (LCD) or light-emitting diode (LED) screens on a boat or plane’s instrument panel while wearing polarized sunglasses. This could interfere with the pilot’s ability to clearly read and quickly respond to the information on the instrument panel. This could also apply to the global positioning system (GPS) and other displays of a car’s dashboard, a smart-phone, an ATM, or a self-service gas pump.

An oddity you may notice while wearing polarized sunglasses is that when you look at your car’s rear or side window from the outside, or perhaps the windows on an office building, you may see splotchy, iridescent spots. When you remove your polarized sunglasses, these spots are invisible.

This effect is created because you are looking at heat-tempered glass. The heat-tempering creates several stress points on the glass, enabling the glass, when broken, to crumble into small, granular chunks, which are safer than splitting the glass into sharp, jagged shards. The stress points also reflect the light in different directions from the parts of the glass that don’t have these stress points. The stress points prevent the polarized lens from filtering out the light evenly across the surface of the glass, creating the splotchy, iridescent effect.

If you are unsure if your sunglasses are polarized, here’s a fun, simple test to see if they are. Hold your sunglasses up to a computer screen, which has an anti-glare coating similar to the anti-glare coating on a polarized lens. Angle your sunglasses about 60 degrees, with one side of the frame at 10 o’clock and the other at 4 o’clock. If the lenses are polarized, they will turn black.

You could also take the test with two pairs of polarized sunglasses – hold one pair at a horizontal (180-degree) angle. Now hold the other pair in front of the first pair, but rotate this second pair of sunglasses a half-turn, till it’s straight up and down, at a vertical (90-degree) angle. You will see that the lenses of both pairs of sunglasses turn considerably darker where the two lenses overlap when they are perpendicular. This is because when you angle one polarized lens to another perpendicularly, they block glare both horizontally (the horizontal pair) and vertically (the vertical pair).

At Zenni Optical, we offer polarized sunglasses in our 1.50 and 1.59 index single-vision and progressive (no-line bifocal) lenses, and in our 1.49 index bifocal lens. All of our detachable sun shades, whether magnetic or clip on, whether standard (the same tint color and shade all the way through) or gradient (the tint is darker at the top, getting progressively lighter toward the bottom) are polarized.

A101204 Sunglasses, Zenni Optical

A note of caution regarding drugstore sunglasses that are not polarized. If the lens is a non-polarized, darkly tinted lens not treated to block UV rays, it could be more dangerous to the eye than wearing clear, un-tinted glasses that have 100-percent UV protection. This is because the dark tint could cause the pupil to dilate, allowing more harmful UV rays into the eye.

You can rest assured that on every pair of glasses Zenni Optical makes, tinted or clear, we include a 100-percent UV-protection coating – for free.

In addition to polarized sunglasses, Zenni Optical also offers a different kind of sunglass lens that sometimes people confuse with polarized: photochromic lenses, which turn dark in the bright sunlight and become clear again in the shade or indoors.

Although you may have heard about a new technology that adds polarization to photochromic lenses, Zenni Optical does not offer these lenses at this time. Our polarized lenses are permanently tinted sunglasses that greatly reduce glare.

  • kevin lefter

    Great Write up… honestly never understood the difference between non-polarized and polarized, Though the difference is pretty “clear”… ok horrible Joke

    Great Job Zenni!

    • http://www.zennioptical.com/ Matthew Surrence

      Thanks for your comment, Kevin!

  • cb

    Do you make prescription polorized mirrored sunglasses? And if so at what starting/typical price? — Thanks!!

    • http://www.zennioptical.com/ Matthew Surrence

      Thanks for your question, CB! Yes, Zenni does offer polarized mirrored sunglasses. Our polarized lenses start at $32.99, for the 1.50 single-vision lens.The mirror finish, which comes in gold, blue, or silver and has the premium oleophobic (fingerprint-resistant) anti-reflective coating, is $19.95.

  • cb

    Oh yeah…another question. Out of pure curiosity what does a polarizing lens do do individual photons? Photons are traveling in a helix, and somehow photons are also traveling in pairs. What meaning does “vertical” and “horizontal” light mean on this scale? — Thankls again!!

  • http://www.zennioptical.com/ Matthew Surrence
  • http://tinyurl.com/ltrw4g3 Joypebble

    Polarized lenses will cut reflected glare from metal surfaces or any other surface by at least 50% in the daylight.

    It will allow you to see into the windshield of the car behind you (when looking in your mirror) and into the rear window of the car in front (assuming that the windows aren’t super deep tinted).

    They are amazing and after a little time diving with them, you will probably be a lifetime convert as I have become.

    You can buy Polarized sunglass lenses which will give you better road definition even when it is raining and misty with poor road conditions because it cuts out the overcast flat glare on the wet roads just enough to give a better ability to see the road lanes and edges on rainy days. (Yes, even without sun being out.)

    They are restful and reassuring in all driving conditions. (At night, they don’t do anything at all except make the scene a little darker.

    No, I don’t work for any company selling Polarized lenses. I just simply love them.

    —GG (a photographer)

  • Gayle Bishop

    Great idea and I’m glad to be aware of it even though it’s so far from its beginning My only frustration with the site is that twice now I’ve received a message that something I’ve chosen won’t work …. but with no help or way to find out what I need to do to correct the mistake. How about a phone number next to the info that an error has occurred. Thanks for reading. I’m still working at ordering some glasses and am forwarding your address to many!!

    • http://www.zennioptical.com/ Matthew Surrence

      Thanks for your comment, Gayle! I was sorry to learn that something you chose on our website wouldn’t work for you. Without more information, I could only venture a guess that the issue might have involved one of two things. It could be your pupillary distance (PD). Each frame has a PD range it accommodates, which you can see if you move your cursor over the picture of the frame or click on Quick View. Perhaps your PD is outside the range the frame you chose accommodates. Or it might have been an issue with the prescription, if you have a bifocal or progressive prescription. To accommodate a bifocal or progressive prescription, the lens height must be at least 30 millimeters. You can also see the frame dimensions at Quick View. If it’s not one of these two issues, or even if it is, you can definitely contact our customer service department for assistance. The customer service phone number and hours are listed toward the bottom of our website. Definitely call customer service for assistance, at (800) 211-2105. The customer service rep who answers will be eager to assist you in resolving this issue.

  • Cherley

    I read this post fully concerning the difference of latest and
    previous technologies, it’s amazing article.

    • http://www.zennioptical.com/ Matthew Surrence

      Thanks for your comment! Glad you liked the article.

  • Jack

    I see that you’ve mentioned in one of your replies that mirror finish is available. However I’ve been looking for the mirror finish option on your order page and just couldn’t find the option. Could you show me how where can I select mirror finish for my sunglass lenses, or are they not available for some lenses? Thanks and cheers!