Glare is the discomfort or loss of vision caused by too much light reaching the eye, often bounced off a surface. Strong reflections during the day and car headlights at night both make it hard to see clearly. This article covers what causes glare, how it affects vision and how to reduce it.
What causes glare?
Glare happens when the eyes receive more light than they can comfortably handle. During the day, the usual sources are reflective surfaces: water, sand, snow, car bodies, windows and wet roads. At night, oncoming headlights are the most common source. Water facing into the sun is one of the strongest reflectors of all.
Do sunglasses block glare?
All good sunglasses reduce brightness, but polarized lenses are the ones designed to block reflected glare. Light that bounces off flat surfaces becomes horizontally polarized, and a polarizing filter blocks that horizontal light while letting the rest through. Non-polarized sunglasses with UV400 lenses still protect against UV, but they don't cut reflections the same way.
Types of glare
- Discomfort glare: a bright light in or near your field of view that makes you squint and lose focus, such as sunlight across a screen.
- Disability glare: light strong enough to reduce what you can actually see, often described as being dazzled. Driving into a low winter sun is a common example.
For driving, a low sun on wet roads is a classic glare situation. Long drives in these conditions cause visual fatigue, and polarized sunglasses make them noticeably more comfortable.
Is glare bad for your eyes?
Glare itself mostly affects comfort and safety: it causes squinting, eye strain and fatigue, and it can hide hazards. The long-term damage people worry about, such as cataracts and macular degeneration, comes from ultraviolet (UV) light, which is a separate issue. That is why the best sunglasses combine polarized lenses for glare with UV400 protection for UV.
