How UV light can affect your eyes
While we often count the days before we can turn our skin from pasty white with a golden summer tan, excessive sun exposure is an area where too much too quickly can be no only inadvisable, but even dangerous.
There are many benefits from bathing in sunlight. It is, for example, known to improve mood making people feel better and giving them more energy. And we all know that sunlight is an essential source of vitamin D which helps build healthy bones.
While medics are very much in favour of daily doses of fresh air and sunshine, soaking up large doses of sunshine over short periods of time is not without risk, especially if you are not used to it.
Your skin can get enough sunlight to promote sunburn in less than 15 minutes, although the effects may be apparent until two to six hours later.
The damage caused to the skin through sunburn and heat rash is well known, but people should also consider the extra eye protection they also need especially while on holiday.
Sunlight is the most common source of high-energy ultraviolet (UV) rays. Ultraviolet (UV) comes from the Latin word 'ultra' which means beyond violet and is the highest frequency of visible light.
Fortunately for us, most it the dangerously high UV beyond violet is screened out by the ozone layer in the Earth's atmosphere.
What UV light does get through is mostly Ultraviolet A (UVA) and Ultraviolet B (UVB), both at the lower end of a spectrum that runs from UVA through FUV (Far Ultraviolet) to EUV (Extreme Ultraviolet).
Scientists have known for some time that exposure to levels of sunlight at the boundary between UVA and UVB light is responsible for skin damage such as sunburn and may even be a significant factor in some skin cancers.
Studies have also shown that exposure to light levels at UVB and above can affect the human eye. UVB in sunlight can cause photokeratitis, more commonly called 'snow blindness' and can also damage vital parts of the eye in the cornea, the lens, and the retina.
All of us are at risk of harm from the sun throughout the year, but the greatest danger is on holiday when we tend to spend much more time outdoors in sunny weather.
Particularly prone to damage are those sunbathers who spend a lot of time on the beach or skiers who go out in the snow. The reflective qualities of sand, snow and water can amplify the effects of UVB radiation and harm unprotected eyes.
Medics say eye damage from exposure to UVB light may occur gradually over time and, once done, may not be reversible. Some people are also more sensitive to UV light than others.
So, when choosing sunglasses, it's important to favour brands that give the best protection against UVB light.
Although UVB may be largely absent from sunlight, it is still worth considering when purchasing sunglasses, especially in conditions such as beach and ski slope where your eyes are likely to be bombarded with bright light.
Protective sunglasses are beneficial to anyone exposed to higher levels of UVB light. Excessive exposure to UV from sunlight or tanning salons can harm the cornea, the refracting surface that focuses light and images to the retina.
Good UV-protective lenses are a must for anyone who uses a tanning salon and for skiers, snowboarders, or mountaineers since UV is more intense at high altitudes, and the snow reflection can double the exposure
You can't tell the amount of UV protection you will get from a pair of sunglasses simply by looking at them. Neither the price nor the lens colour, give any indication either.
Most people in the market for UV sunglasses will have to rely on the label to explain how much protection they offer. There are industry standards, but it is worrying that not all manufacturers adhere to them.
Many modern sunglasses will have a sticker or label claiming 100% UV protection, but they won't protect eyes from the reflected light that arrives around the lens.
It is a good idea to wear a wide-brimmed hat as well as sunglasses. The hat will block about half of the UV rays and limit the rays that hit the eyes from above or around the sunglasses.
Sunglasses with acrylic plastic lenses will give slightly higher protection than glass which is transparent to UVA, unlike the conventional acrylic plastic used for lenses.
Some plastic lenses, such as polycarbonate, block most UV rays and many modern sunglasses have a protective coating that will block UV light completely.
People who work or play in the sun for long periods will be at the greatest risk which sun-related eye problems increase for those who have had cataract surgery or take certain medicines that increase the eye's sensitivity to light.
It's is important to have a complete ophthalmic examination at least once a year to ensure your eyes stay good and healthy.