Promotion: Winter sun
If you're off to find sunshine this winter don't forget to pack the right sunglasses.
Many of us are looking forward to hitting the ski slopes this winter. Others will be escaping the wintry weather for sunnier climes. Either way, it's vital to protect your eyes from the sun.
Over-exposure can cause serious damage due to the ultra violet rays. These are most prolific when the atmosphere is very clear - such as on the ski slopes or in the tropics.
While most people know how important it is to keep skin protected from the sun, few realise how damaging UV rays can be to eyes. You can develop a painful form of sunburn called photokeratitis.
Sufferers are often unaware this is happening when out in the sun as the effects may take up to 12 hours to develop.
Long-term exposure can cause cataracts and even ocular tumours if eyes are not protected with the right kind of sunglasses. Always read the label and choose the maximum protection factor available.
Rays on the piste are heightened by glare, which occurs when light is intensified as it reflects off the shiny surface of the snow. A sandy beach or calm sea will have the same effect.
Polarised lenses reduce this by using a layer of iodine crystals to absorb the glare. Non-polarised sunglasses have minimal effect, even though they will reduce visible light.
Although perfect for alpine views, particularly active skiers may find polarised lenses unsuitable for skiing as they can reduce the definition of the snow's surface.
Budget sunglasses can be a false economy - many actually cause the pupil to dilate, increasing the amount of UV light filtering into the eyes.
You'd be surprised how many still choose a cosmetic pair over safety, when it is easy to have the best of both.
1. Contact lenses offering UV protection do not cover the whole area of your eye, so should be worn with sunglasses
2. The larger the sunglasses lens, the more protection your eyes will be given, as there's much less chance that light will filter in through the sides