Polarized sunglasses are eyewear made with special lenses that reduce reflected glare from surfaces such as water, snow, and glass. Polarized sunglasses can be especially useful in situations where you need to see clearly and avoid hazards.
Despite what some people think, polarized lenses do not protect against ultraviolet (UV) light from the sun. Both prescription and non-prescription lenses can be polarized.
This article explains how polarized lenses work. It also lists some of the benefits and drawbacks of this type of protective eyewear.
What Do Polarized Sunglasses Do?
Polarized sunglasses are designed specifically to reduce glare so that you can see clearly in situations where you might otherwise squint or be blinded by reflected light.
Glare is caused when light hits a reflective horizontal surface, causing light beams to be scattered horizontally. This can overwhelm photoreceptors in the eyes, including rods that allow you to see in darker conditions and cones that allow you to see color.
Glare can dramatically impair your vision, making colors harder to distinguish and even "whiting out" your vision entirely. Squinting is your body's natural response to this, designed to prevent damage to the rods and cones from excessive light exposure.
Polarized lenses counteract glare by applying a special chemical to the lenses in a vertical pattern. The vertical orientation of the chemical application is what blocks the horizontal light.
This chemical process can be applied to the surface of the lenses only (for less costly sunglasses) or sandwiched between two layers of lens materials (for costlier sunglass brands).
A high-quality pair of sunglasses will almost invariably have polarized lenses.
What Are the Benefits of Polarized Sunglasses?
Polarized lenses do not block UV light from the sun which can damage the eyes. They are simply designed to prevent glare, not only during the day but possibly at night as well.
The polarization of lenses is beneficial in that it:
Polarized lenses are available in a variety of colors, ranging from very dark hues to very light hues.
The color or darkness of the lens doesn't mean the lenses are "better" or "worse" at blocking glare. Both can be equally effective.
With that said, some colors are more useful in certain situations. For example:
Because of the chemical process involved in making polarized lense, there are no true clear polarized lenses. There is always some degree of tinting, even if the shade is light.
When Should You Wear Polarized Sunglasses?
Glare can be dangerous, especially when driving because it distorts the true color of objects and makes objects harder to see. Glare has been linked to many pedestrian deaths and traffic accidents.
Polarized sunglasses can be especially helpful in situations like:
To check if your lenses are polarized:
Disadvantages of Polarized Sunglasses
Polarized lenses aren't right for everyone. There are three specific situations in which they may be more problematic than useful:
Polarized Sunglasses
Reduce glare from reflected surfaces
Darkness or lightness of the lens does not affect how well they work
Can make digital interfaces look fuzzy and difficult to read
Improve color perception
Can cause the dimming of headlights at night
Usually made with UV-protective lens material
Tend to be costlier
Non-Polarized Sunglasses
Reflect all light but do not reduce glare
Darker lenses work better than lighter lenses
Do not make digital interfaces fuzzy but can make them too dark to read
Obscure color perception
Cannot be used for nighttime driving
May or may not be made with UV-protective lens material
Tend to be cheaper
Summary
Polarized sunglasses are designed to reduce glare caused by light this is reflected off horizontal surfaces. The chemical processes used to make the lenses are vertically oriented.
Polarized lenses are helpful for reducing glare and increasing color perception when you are driving, boating, or playing sports.
Polarized lenses aren't right for every situation. If you're driving at night or using LCD devices, the lenses cause dimming and blurring.