Buying sunglasses online is quick, easy and especially cost effective when compared to buying on the high street. There are an enormous range of prescription sunglasses and current season, high fashion designer glasses available. But even cheap designer sunglasses need to safely protect your eyes from dangerous UV radiation, so you must check carefully at an optician’s website before making a purchase.
The best online opticians will state the level of UV protection offered by all the sunglasses they offer. Generally, this is identified as protection to UV400. But what does this mean and is it the required level required to safely protect your eyes against exposure to the sun’s different levels of radiation?
Aside from man made tools and products, the sun is the earth’s primary source of Ultraviolet radiation (UV), which is divided into at least three different categories based on wavelength:
Wavelengths:
UVA – 320-400 nm
UVB – 280-320 nm
UVC – 100-280 nm
UVA – 320-400 nm are only slightly affected by ozone levels.
Most UVA radiation is able to reach the earth’s surface and can contribute to tanning, skin aging, eye damage, and immune suppression. UV 400 Protection lenses are engineered to block 100% of all harmful blue light up to 400 nanometers
UVB – 280-320 nm are strongly affected by ozone levels.
Decreases in stratospheric ozone mean that more UVB radiation can reach the earth’s surface, causing sunburns, snow blindness, immune suppression, and a variety of skin problems including skin cancer and premature aging.
UVC – 100-280 nm are very strongly affected by ozone levels
The levels of UVC radiation reaching the earth’s surface are relatively small.
All UV radiation can be extremely damaging, which has led many manufacturers of sun screen and sunglasses to offer products that protect against both UVA and UVB wavelengths.
Solar UV radiation levels are highest during the middle of the day, and in total, almost half the daytime total UV radiation is received during the few hours around noon.
Short and long-term exposure to UVA and UVB rays can cause significant damage.
Short-Term Effects of UV Radiation
A brief exposure to UV radiation, usually when combined with cold wind and snow, is likely to lead to Photokeratitis, which is an inflammation of the cornea. Like a “sunburn of the eye”, it may be painful and create symptoms including red eyes, a foreign body sensation or gritty feeling in the eyes, extreme sensitivity to light and excessive tearing. Fortunately, this is usually temporary and rarely causes permanent damage to the eyes.
Long-Term Effects of UV Radiation
Long-term exposure to UV radiation can be more serious. Exposure to small amounts of UV radiation over a period of many years may increase the chance of developing a cataract, and could cause irreversible damage to the retina. Cumulative damage by repeated exposure may contribute to chronic eye disease, and increase the risk of developing skin cancer around the eyelids.
It is always strongly recommended to wear quality sunglasses that offer protection to UV400 level, which will block out 99 – 100% of both UV-A and UV-B radiation and screen out 75 – 90% of visible light. Wrap-around frames can provide additional protection.
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