Sunglasses are worn primarily to eliminate the discomfort and disabling effects of bright light and to protect against ultraviolet and infrared radiation. The need for sunglasses varies because people differ in the extent to which they tolerate bright light and in their occupational and recreational activities.
Sunglasses are designed for outdoor daytime wear in bright sunshine or where there is glare. They should be worn when bright sunlight causes watering of the eyes, squinting or excessive blinking.
Sunglasses are essential during periods of prolonged exposure to sunlight. Besides visible light, sunlight contains two powerful, invisible forms of radiation - ultraviolet and infrared. Continued exposure to these rays can cause serious eye damage.
Bruce recommends that people who spend most of their time outside or who work near snow, water or sand should wear sunglasses that filter out both ultraviolet and inferred rays. Because the effects of exposure to UV accumulate over a person's lifetime, it is important for Children as well as adults to wear eye protection.
Sunglasses should not be worn at night, particularly while driving. This is because in the dark they can reduce vision to dangerously low levels. A driver could easily miss seeing a pedestrian or parked car.
If you feel that need to wear sunglasses continually for comfort, you should consult your optometrist - you may have a problem with your eyes or vision that requires further investigation.
There are different kinds of sunglasses lenses.
Tinted - Made of glass or plastic, tinted lenses come in variety of shades. To be effective they should screen out 75 to 90 percent of available visible sunlight. Grey tints do not affect the colours you see and are the best choice where colour accuracy is important. Glass lenses with green tints are usually the best infrared filter. Lightly tinted "fashion" lenses do not screen out sufficient light to be properly classified as sunglasses.
Polarising - Usually plastic polarising lenses are effective in combating the glare caused by light reflected from the road or from water. They screen out ultra violet rays. Prescription polarised lenses are also available. Drivers should note that dark blotches appear on some safety windscreens when looking through polarising lenses.
Photo Chromatic - commonly called sun- sensitive or light sensitive lenses, photo chromatic lenses darken or change colour as the sun gets brighter. To ensure sufficient darkening in sunlight, only quality photo chromatic lenses should be worn and 75 to 90 per cent of available sunlight should be screen out.
Reflecting - A thin metallic coat is combined with tinted lenses to produce a mirrored appearance. They are designed for wear under intense glare such as light reflected from water or snow. Some absorb both ultra violet and infrared rays.
Make sure that the lenses:
Sunglass standards became law in Australia on 1 October 1985. Under the standard, sunglasses are divided into three main categories and labelled for information of consumers.
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