Sight and the sun

Our ability to see depends entirely on light, yet certain kinds of light can actually be bad for our eyes. One kind of light - ultraviolet (UV) radiation - appears to contribute to a variety of disorders, including cataracts, cornea damage and, perhaps most importantly, age-related macular degeneration (AMD). One study has shown that spending five or more hours outside every day in the summertime during your teens and early adult years could increase your risk of AMD by as much as 50 per cent, which goes to show that it’s never too early to start looking after your sight! Below you’ll find out what UV is, what it does and how to stay safe in the sun.

UV

Ultraviolet radiation is a kind of invisible light whose most common source is the sun. There are three types of UV - UV-A, UV-B and UV-C.

Here on Earth, UV-C rays don’t pose any threat, as they are absorbed by the upper atmosphere and so don’t reach us. Most of the UV that reaches down here on the Earth’s surface is UV-A. This can penetrate deep into the eye, causing damage inside it. It also causes the skin to tan, and is thought to contribute to ageing of the skin and skin cancer.

Most UV-B is also absorbed before it can reach us, but some does penetrate the atmosphere, and it is even more harmful than UV-A. It too can cause sunburn and skin cancer, and is absorbed in the eye by the cornea and lens, causing damage to these structures.

When it’s strongest

Because of its association with sunburn, it’s tempting to think of UV as only being present on sunny days. It is true that it tends to be at its strongest when the sun is shining brightly, but it is actually present all the time during daylight hours and can do damage even when it’s cloudy!

You’re at greatest risk of over-exposure to UV:

• Between the hours of 10am and 2pm
• During the warmer months of spring and summer
• When you’re on or near water, sand, snow or any other highly reflective surfaces. For example, you can easily absorb a lot of harmful UV when you’re under a sun umbrella, if you’re surrounded by white sand and water
• At high altitudes
• The closer to the equator you are
• When you're taking certain prescription drugs that increase your sensitivity to UV

How to avoid damage

The best way to avoid damage to the eyes from UV is to stay out of the sun altogether, but failing that, wearing a hat with a brim or a peaked cap could shield you from as much as 50 per cent of the sun’s UV. It is also important to wear a pair of good-quality sunglasses, as they can block between 99 and 100 per cent of UV radiation. Price is no guarantee of quality; the important thing to look out for is that your sunglasses carry the CE marking, which means they conform to European safety standards.

Sunglasses

These are some simple guidelines to follow when you buy your next pair of sunglasses.

If they don’t carry the CE marking, don’t buy them! Although it’s illegal to sell non-UV-protective sunglasses, trading standards officers still find them on sale. Yet wearing them could be worse than not wearing any at all. Normally, the eye protects itself from bright light by constricting the pupil and closing the eyelids, but when sunglasses are worn, the pupil doesn’t constrict and, if the glasses are very dark, the pupil may dilate. This allows more harmful UV into the eye when the sunglasses are not UV protective.

Your sunglasses should block out 75-90 per cent of visible light and 99-100 per cent of UV rays.

Wraparound sunglasses prevent light - and UV - from getting behind your sunglasses and into your eyes.

Shades come in lots of different colours, but the best colours of lenses for protecting your eyes are brown, amber, green or grey.

Check that the lenses don’t have any distortions or scratches.

Shatterproof plastic lenses are much safer, especially if you’re buying sunglasses for a child.

Light-coloured eyes - blue, grey or green eyes - need more protection. Children’s eyes are more vulnerable than adults’, so it’s vital that those responsible for children make sure they wear sunglasses too. If you’re buying them for yourself, why not buy your child a pair too?

Support the Shades Day campaign promoting the need to "Look cool and stay safe"!