When purchasing a new pair of sunglasses, you will typically encounter the question – do you want polarized or non-polarized lenses? Despite this common question, many people do not know the difference between the two or if one type of lens is more beneficial than the other.
We asked Robert Dimick, Optical Shop Director at Dean McGee Eye Institute, to clear up the confusion and provide more information on polarized versus non-polarized sunglasses.
Polarized vs. Non-polarized Sunglasses
In general, the ability to filter light is the main difference between polarized and non-polarized sunglasses.
“Polarized lenses are designed to filter out light and reduce glare from reflective or bright surfaces,” Dimick says. “Whereas, non-polarized lenses offer protection from light, but do not have a built-in filter to reduce glare.”
What is Glare?
When light waves from the sun reach the earth, they are scattered or absorbed in different ways depending on the surfaces or materials with which they interact. Most of the time, the light is scattered in all directions. However, should the light hit a reflective surface such as snow, water, metal, or glass at just the right angle it bounces off the surface one direction (horizontally) creating an intense area of brightness known as glare. Such glare can cause eye fatigue, reduce visual acuity, and diminish depth perception.
What are Polarized Sunglasses?
Polarized sunglasses receive an anti-glare coating to block the bright light that reflects horizontally off objects such as water or snow. In addition, they are also typically made to block harmful ultraviolet (UV) rays.
So how do polarized lenses work? During the manufacturing process, a special type of crystal or dye is applied to the lens in millions of parallel rows. These rows block horizontal light but let vertical light pass through. The result is comfortable, glare-free vision.
Aside from eliminating glare, polarized lenses can improve clarity and contrast making images appear more crisp and vivid. This can be noticed specifically with colors. For example, green grass will look greener, and blue skies will look bluer.
What are Non-polarized Sunglasses?
Non-polarized sunglasses contain dyes and pigments to block UV rays, reduce the overall intensity of light, and keep your eyes protected from the sun, but horizontal light associated with glare is still able to pass through. Therefore, non-polarized sunglasses will not alleviate issues with glare.
Who Should Use Polarized Sunglasses?
Polarized sunglasses are ideal for people who spend a great deal of time outdoors, especially around water or in the snow, or who drive most of the day. They are also beneficial for anyone who wants to reduce eyestrain from glare or who enjoys viewing the outside world more vividly..Examples of people who most commonly use polarized sunglasses include fishermen, runners, motorcyclists, and beach goers.
“Whether for work or play, these sunglasses can help you feel comfortable and provide better clarity as you go about your day,” Dimick says. “Polarized sunglasses are helpful all year round, whether you are around water or snow, or even outside on a cloudy day.”
When Should You Not Use Polarized Sunglasses
As beneficial as polarized lenses can be, there are times when you should not use polarized lenses. Wearing polarized lenses may be dangerous for skiers as they can make it difficult to distinguish ice from snow or for pilots or heavy machine operators as polarized lenses can make it hard to view instrument panels. In such situations, non-polarized lenses are the better option.
Even in everyday situations, there are times when polarized lenses are not ideal. For example, LCD screens, such as those found on phones, digital watches, and car dashboards, can be difficult to read while wearing polarized lenses.
Why is this? LCD screens often contain a polarized filter that helps you see the screen in bright conditions by blocking vertical light and emitting horizontal light. However, polarized sunglasses block this horizontal light. The result is the sunglasses and LCD screen work against each other to create darkened images that are hard to see.
To alleviate this problem, remove the sunglasses or rotate the screen 90 degrees so the direction of the light waves from the screen are now vertical and can be seen through polarized lenses.
Do Polarized Lenses Have any Notable Health Benefits?
Some may view polarized sunglasses as nothing more than a personal preference, but there are benefits to having these types of lenses.
“Blinding sun glare can cause accidents, snow blindness, and can even sunburn your eyes. Long-term exposure to sun glare has been known to cause cataracts,” Dimick says. “Thankfully, polarized lenses can shield you against the dangers of intense glare.”
Although polarized lenses can help with glare, without additional filtering they will not protect your eyes from harmful UV rays. For that, you will need polarized sunglasses that include UV protection.
“UV400 protection provides our eyes with the highest level of protection. It blocks out virtually 100% of all harmful UV rays,” Dimick says. “Polarized lenses use a special film to further filter reflected light and reduce glare. Sunglasses that have both give you the best overall protection.”
