Glare can be caused by reflections of light coming off the waters surface, off a ski slope, from on-coming car headlights, floodlighting or the sun itself. It can reduce visibility, cause distractions and even be very dangerous. Glare can also be particular problematic to cataract patients or those who have recently undergone laser eye surgery.

Glare is defined as the contract lowering effect of stray light in a visual scene. Glare can cause a veil of luminance that reduces contrast and therefore decreases the visibility.

Glare can be divided into two different types:

• Discomfort glare which refers to the effect you experience when the overall illumination is too bright as anyone who has seen a snow field in bright sunshine can testify to.
• Disability glare which occurs when the visibility of an object is reduced due to a bright light source. This has the effect mentioned above of reducing the contrast and therefore general visibility.

Glare is particular a problem for people such as drivers on long flat roads when the sun is very bright and can be potentially dangerous. Similarly, fishermen can experience glare by light reflecting off the water and as previous mentioned, snow sports with the bright reflections from the snow.

Glare can be significantly reduced or outright eliminated through the use of polarized sunglasses. These can reduce or remove glare from vision and allow wearers to gain a more acceptable level of contrast.