All sunglasses are designed to reduce brightness, but standard tinted lenses don’t eliminate harsh glare and reflection. Polarised lenses provide 100% protection from glare and UV rays but the chemical filter in the lenses of polarized sunglasses is designed to absorb horizontal light waves, while still allowing vertical waves to pass through. Because light only travels in one direction through polarized lenses, glare is eliminated.
When sunlight reflects off horizontal surfaces like tarmac, snow, water, pavement or even grass, much of the light is concentrated in horizontal waves. This horizontally polarised light is seen as annoying glare, and masks useful light which is travelling in the vertical direction. The result is that you can’t see properly and you tend to squint or close your eyes – this would diminish the enjoyment of a spectator or someone playing golf, for example; but for a sailor or driver the consequences could be far more serious.
It is important to be aware that you do not even need a sunny day; you can get glare on overcast days because light still reflects off horizontal surfaces and becomes concentrated in the horizontal direction. Polarised sunglasses have a special polarising filter in the lens that blocks horizontally reflected glare and lets in the vertically travelling light that the eye can use. The resulting benefits perceived by the wearer are that compared to non-polarised lenses everything looks clearer and the eyes feel more comfortable, reducing eye fatigue – a significant benefit to the sports person and the driver.
Though polarised sunglasses improve comfort and visibility, there are some situations where the reflected light does help such as seeing ice on the road. In addition, polarised lenses will allow you to see the underlying pattern in toughened glass such as car windows (windscreens are usually laminated except in some older classic cars). Occasionally some previous-generation LCD displays like those found in older sat-navs, mobile phones and equipment are hard to see through polarised lenses; this problem is being addressed by many of the manufacturers and most modern devices can be seen without any difficulty.
Please contact your local branch of Rawlings Opticians for all the advice that you need on the best lens choices.