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Are cheap sunglasses effective?

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Posted June 27, 2017

Ahead of National Sunglasses Day on Tuesday, 27 June University researchers assessed differently priced children’s sunglasses to find out how effective they are at blocking both Ultra Violet A (UVA) and Ultra Violet B (UVB) rays as many promise to block “100 percent” of rays.

UVA rays tan your skin but also cause premature ageing and can accelerate the development of age related illnesses. They cause damage over a long period and excessive exposure can damage eyesight.

The degree to which a material protects the skin / eyes from UV rays is given as its UV protection factor that is predominantly influenced by UVB transmission through the material. Responsible for causing sunburn, UVB rays can damage eye tissue with unprotected exposure.

Kitemark

The British Standards Institution (BSI) is the national standards body of the United Kingdom. BSI produces technical standards on a wide range of products and services, and also supplies certification and standards-related services to businesses. The BSI Kitemark™ is a quality mark owned and operated by BSI.  It is one of the most recognised symbols of quality and safety.

The British Standards Institution tests sunglasses to a particular standard (BS EN 1836:1997) to meet this standard sunglasses must have values less than 1% when it comes to UVA and UVB transmission (the percentage of UVA and UVB rays passing through the lens).

Dr Laurence Tidbury from the University of Liverpool’s Directorate of Orthoptics and Vision Science, and Dr James Hobson from the Department of Chemistry tested eight different pairs of children’s sunglasses, which, despite ranging in price, claimed to block 100 percent of UVA and UVB rays.

UV rays

To test the sunglasses the researchers measured the transmission of UV light by placing a strip of the sunglasses material into a machine that typically measures the absorbance of light by chemical compounds. They found that all of the sunglasses tested met the BSI standard and allowed through less than 0.5% of the UV rays: the transmission of UVA and UVB in turn were below 0.5%.

Dr David Newsham, Head of the University’s Directorate of Orthoptics and Vision Science, said: “The sun’s UV radiation can cause an onset of cataracts, macular degeneration and even growths on the cornea.

“You should always wear protective eyewear any time your eyes are exposed to UV light, even on cloudy days and during winter months. Essentially exposure to UV light will age your eye faster.

“Look for quality sunglasses that offer good wrap around protection. Sunglasses should block out 99 to 100 percent of both UVA and UVB radiation. Check to make sure your sunglass lenses are perfectly matched in colour and free of distortions and imperfections such as scratches.”

Source: University of Liverpool

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