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UV Protection

You wouldn't expose your skin to sunlight all day long with no protection, so why do exactly this with your eyes ? This section of the Eyewear Systems web site provides essential information about protecting your eyes (and it's a great ice-breaker when you want to chat someone up !).

Long-term exposure to UV rays can damage the eye’s surface as well as its internal structures, sometimes contributing to cataracts (clouding of the lens) and macular degeneration (breakdown of the macula). Ophthalmologists and optometrists now recommend wearing sunglasses and a brimmed hat whenever you’re in the sun long enough to get a suntan or a sunburn, especially if you are at a high elevation or near the equator.

What is UV ?

UV (Ultraviolet Radiation) consists of the short, invisible rays from the sun that reach the earth's surface. These rays contain three separate bands: UVA (315-380 nm), UVB (290-315 nm) and UVC (100-290 nm). UVC rays are absorbed by the earth's atmosphere and do not reach the earth's surface and therefore do not relate to sunglass performance. UVB rays are the " sunburn " rays. Exposure to UVB rays can potentially produce harmful effects to your eyes and may be associated with cataracts and retinal damage. UVA rays are mostly absorbed within the lens of the human eye, debate over the potential effects of UVA exposure continues within the industry. Sunglass standards place limits on UVA and UVB exposure . UV radiation is strongest at high altitudes, low latitudes and in open or reflective environments (sand, snow or water).

Factoids

1 Ultraviolet rays are the most dangerous type of radiation. The majority of UV rays are absorbed by the atmosphere, but the quantity filtered is very variable. Those people nearest the equator and at high altitude will be in a thinner atmosphere. The effects of UV radiation are increased if reflected by surfaces such as snow, sand and water .
2 Water reflects approximately 20% radiation and sand reflects approx 10%. Snow reflects 85% and the intensity of the UV rays increases by about 10% with every 1,000 metres of height gained. It is advisable to have high wrap glasses in the mountains. The higher the relative humidity, the more dangerous the radiation.
3 Children, especially very young children have more fragile eyes than adults. UV absorption is total in babies and high under 13 years.
4 The tint in sunglasses is protecting you against dazzle, which is necessary in itself but dazzle is not harmful to the eyes. Lenses can give total UV protection even when clear. Heavily tinted glasses can do more harm than good as they cause the pupil of the eye to dilate so much, allowing in a lot of UV if the glasses do not have an adequate UV rating.
5 Lenses that are declared as optically correct are able to transmit a laser beam through them to a centred target with complete accuracy, and not deflect the beam off at an angle. Some lenses cannot do that, which can result in you misjudging your step when walking and making errors when driving.

The good news is that sunglasses don’t have to be expensive to protect your eyes. Unfortunately, a high price is not always a guarantee of high quality and protection. Part of the difficulty is that standards and labelling regarding UV protection are voluntary, not mandatory—and can be confusing. So here is the bottom line:

Look for UV protection

Don’t be deceived by colour or cost. The ability to block UV light is not dependent on the darkness of the lens or the price tag. While both plastic and glass lenses absorb some UV light, UV absorption is improved by adding certain chemicals to the lens material during manufacturing or by applying special lens coatings. Always choose sunglasses that are labelled as blocking 99-100% of UV rays. Some manufacturers’ labels say “UV absorption up to 400nm.” This is the same thing as 100% UV absorption - and it's what the term "UV400" means ! And as for the darkness of the lenses ? Darker lenses may put less strain on your eyes, but they may also let your pupil dilate more, letting more of the UV that comes in from the sides of the sunglasses through as a result.

Wear wraparounds or fitovers

Fitovers are sunglasses that can be worn over your regular prescription glasses and they often provide a wraparound feature.
Wraparounds offer added protection over standard sunglasses. Sunglasses that wrap around the temples prevent the sun’s rays from entering from the sides. Some studies have shown that enough UV rays enter around standard sunglass frames to reduce some of the protective benefits of the lenses.
Ensure they block enough light

To what standards are sunglass lenses measured?

Depending on where they are sold, sunglass lenses must meet the requirements of the standards listed below:

- European Norms - EN 1836-1997
- American Standards - ANSI Z80.3 - 2001
- Australian Standards - AS 1067.1 - 1990 (from October 2004: AS/NZS 1067 - 2003)

For Driving and Road Use:
Filters suitable for road use and driving shall be in accordance with specific requirements:

- Spectral Transmittance European, American, Australian/New Zealand standards must be > 8%
- For EN and ANSI the spectral transmittance between 500 nm to 650 nm must be > 0,2 x tv.
- For AS/NZS the spectral transmittance between 450 nm to 650 nm must be > 0,2 x tv.

Recognition of Signal Lights:

Now you've read and absorbed that lot, you are ready to learn all about sunglasses design and construction - click here !

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