Eye Health Central

How Polarised Sunglasses Reduce Glare

Polarised Sunglasses Explored

polarised sunglasses glare

Polarised sunglasses have been increasingly popular for decades with professional drivers, athletes, and people who spend significant time outdoors. Polarised lenses for sunglasses operate to eliminate glare for skiers, bicyclists, sailors, kayakers and people who enjoy fishing. Even commuters who drive to and from work and school find polarised sunglasses particularly helpful in reducing or eliminating glare from a road's surface or the paint on another vehicle.

Light Diffusion

Once it hits our atmosphere, the light from the sun scatters in all directions, but when it hits a flat surface like a road, the hood of a car or a window, that light becomes polarised. What that means is that the light travels in a brighter and more consistent direction. That direction is almost always horizontal and right into our eyes. That is when horizontal glare becomes involved. As a result of diminished visibility, the risk of harm to a person or property dramatically increases, even if a person is wearing regular sunglasses.

What Is Polarisation

Ordinary sunglasses, without any filtering, fail to block glare. They only reduce the intensity of both horizontal and vertical light. When the lenses of sunglasses become polarised, a special chemical is either applied to those lenses or included during the injection molding process. That chemical operates to filter the light that passes through the lenses. When sunglasses are polarised, that filter allows light to pass through the lenses vertically. Horizontal light is absorbed, and it isn't allowed through. What the eye and brain see is likely to be a little bit darker than usual, but the acuity and detail of the image will be enhanced.

What Are The Advantages of Polarised Lenses

Most people are aware that wearing 100% UV protection sunglasses is advisable to protect our eyes from UV rays. What many people don't realise is that polarised sunglasses doesn't mean they will protect your eyes from UV rays as UV and polarisation are separate things however polarised lenses will help you with: 

  • Reduce glare
  • Enhance safety
  • Improve visual clarity
  • Reduce eye strain

Here is a little in-depth explanation

Glare Reduction and Enhanced Safety

When driving on a motorway on a bright and sunny day, fixed objects that are in the distance might appear to be hazy or smoky. Vehicles that are traveling in your direction and approaching from the opposite lanes of traffic will probably be reflecting annoying and distracting sunlight. That light can even be blinding. Sunglasses with polarised lenses will block the glare from that reflecting light. Your vision and perception will be vastly improved. The same issues arise on water surfaces when boating or fishing. Fish habitats, underwater obstacles, and dangers are more easily identified, and safety on the water is vastly improved.

Improved Sight Clarity

When there is no more glare, vision clarity is remarkably improved. The contrast level is sharp and defined. Colour visibility is significantly better too. Polarised sunglasses are also recommended by doctors for people who have had cataract surgery. Those doctors want their patients to try to avoid bright light.

Reduced Eye Strain

Bright light and glare can be overbearing and result in eyestrain. That wear and tear on your eyes can be relieved with polarised sunglasses. You can avoid redness, squinting, eye fatigue, headaches, and even migraines with polarised sunglasses. In bright daylight conditions, your eyes are far more likely to feel comfortable.

Reduce Glare Behind You Too

A word on rear glare. Glare and reflections can distract you when they are behind you too. Anti-reflective coating is available for the backs of your lenses for purposes of reducing or eliminating distractions when the sun is behind you.

Skiing and Snowboarding

Some skiers and snowboarders will only wear polarised glasses or goggles. They can reduce glare drastically, but in snow conditions with varying shades of white and light, the visual definition of ice and snow might be lost. Subtle changes in elevation might also be difficult to distinguish.

Progressive and Photochromatic Lenses

If you are still wearing bifocals or even trifocals, it is probably time you took a look at progressive lenses, these lenses look exactly like regular lenses as they have no demarcation lines. The power of the lens progresses from top to bottom so you can "alter" the power you need by looking through the glasses at a slightly different point. Nearby objects, objects at intermediate distances and even objects that are far away are seen clearly and without any line interference from lenses. Progressive lenses are available for polarised sunglasses too. You can even be fitted with photochromatic polarised glasses that darken on their own as conditions get brighter. You might have heard of these referred to as transition lenses. These might not be recommended for driving, but you can check with your eye care professional.

Ultraviolet Rays

Polarised sunglasses and sunglasses that provide you with ultraviolet rays (UV) protection are two different creatures. Sunglasses that block UV rays are strongly recommended by the AOP. Exposure to UV rays can result in serious eye damage like cataracts, pterygium, and sun-burnt eyes that can cause temporary blindness or even eye cancer. Beware of simply wearing dark glasses, they very likely will not offer UV protection and it's unlikely that they're polarised. More UV damage can be caused with those glasses than by not wearing any sunglasses at all. 
Always check your polarised sunglasses offer the appropriate amount of UV protection!

Polarised Night Driving Glasses

Polarised night driving glasses are not the same thing as polarised sunglasses. When people refer to night driving glasses, they are usually talking about yellow polarised lenses. They might be of help in tolerating headlight glare, but it's unlikely that they will improve a driver's vision in the dark.

Factors to Consider When Buying Polarised Sunglasses

As per the AOP, the following are some important factors to consider when buying sunglasses:

  • Pay close attention to the merchandise. Buy a good-quality and well-fitting pair of sunglasses with the CE mark. If there is no sticker or tag that tells you what kind of protection you are getting with the sunglasses, don't buy them You will want them to have a sticker or a tag attached that indicates how much protection the sunglasses offer. They should be labeled polarised with UV 400 or 100 percent UV protection.
  • If you are a contact lens wearer, even if your contact lenses offer UV protection you will still need to wear sunglasses
  • Size does matter. The larger the lenses on the sunglasses, the less potential there is for damage to be caused by UVs to a person's eyes. If you buy wraparound sunglasses, they protect against UVs entering from the side.
  • Children should be wearing sunglasses - It is estimated that 80% of UV damage happens before the age of 18, yet a recent poll found that only a quarter of children are wearing sunglasses with UV protection and a third (31%) rarely or never do wearing sunglasses. Darker isn't necessarily better.
  • Darker lenses do nothing to protect against UVs any better than lighter coloured lenses.
  • Colour is irrelevant too. Colour might increase contrast, but it does nothing to block more sun.
  • Polarisation cuts glare, but it offers little protection from the sun.

Disadvantages of Polarised Sunglasses

Although the advantages of polarised sunglasses far outweigh their disadvantages, here are a few of the downsides of polarised sunglasses.

  • LCD screens can disappear at certain angles. Some professionals like airplane pilots are forbidden from wearing polarised sunglasses because of LCD screens in cockpits.
  • The Lack of Contrast. Slight variations in contrast and height can be eliminated. 
  • Not all polarised glasses offer the correct amount of UV protection. Always look for the CE mark and the amount of UV protection offered. 
  • Saltwater. If you live in a coastal area, saltwater exposure can result in the coating used for polarisation eventually cracking, peeling and failing. Human sweat on the lenses of polarised sunglasses can have the same effects.

If your eyes get fatigued easily in the light, polarised sunglasses are a good option. When wearing them outside, expect your vision to be considerably sharper. Polarised sunglasses can help improve your overall safety while also improving your performance in a variety of activities. 

Our eyes and sight are of vital importance. That's why taking appropriate measures to protect them makes sense. Ultimately it's a personal choice as to whether polarised sunglasses are a good option for you. Millions of people prefer them to traditional types of sun protection, especially for sport. 

Author: John Dreyer Optometrist Bsc(Hons), MCOPTOM, DipCLP
Created: 24 May 2023, Last modified: 20 May 2024