Block the rays: The sun can be your worst enemy. Illustration: Suman Choudhury

Skiing is one of our favourite winter sports, but it has its hazards ? and not just broken bones and wounded pride. Brilliant alpine sunshine combined with whistling winds and flying ice particles can wreak havoc on unprotected eyes. Snow blindness, caused by ultraviolet light burning the cornea, is one of the most painful eye injuries of all.

Fiona Sweetman, 33, experienced the agony of snow blindness during a skiing holiday to La Thuile in the Italian Alps last winter.

?It was a lovely sunny day and I lost my sunglasses in a fall,? says Sweetman, the marketing manager for the Ski Club of Great Britain. ?I skied all day without any glasses and, by evening, my eyes were red and sore.? The next morning, her eyes were swollen, her vision blurred and her eyelids glued together.

Snow blindness is a bad case of eye sunburn. Blood vessels in the cornea, the membrane that covers the white of the eye, dilate to allow blood and fluids to bathe the damaged area, causing inflammation and pain. The epithelium, the outermost layer of the cornea, is 400 times more sensitive than skin.

Fortunately, after 48 hours, the swelling and discomfort subsided, but Sweetman?s skiing holiday was ruined. ?I will never make that mistake again,? she says. ?These days, I always carry a spare set of glasses and goggles and I never ski without protecting my eyes.?

Michel Guillon, an eye specialist who runs a skiers? vision clinic in London, says that many underestimate the power of the alpine rays. ?The higher you go, the thinner the atmosphere and the more ultraviolet light you are exposed to.?

UV intensity increases with altitude by 10 per cent to 16 per cent every 1,000 metres. In addition, snow reflects up to 85 per cent of the UV light straight back into the eye.

?Choosing the right sunglasses or goggles is as important as choosing the right skis or boots,? says Dr Guillon. He says the best way to protect eyes while skiing is to buy a pair of well-fitting ski goggles. These should fit snugly, as they are designed to protect your eyes during a fall.

Goggles are ideal for contact lens wearers. Those with blue or green lenses are best when the sun is out. Pink and orange lenses pick out contrast and are the best option on cloudy days. Lenses should offer 100 per cent UV protection. Glasses or goggles should be worn throughout the day, even if it is overcast, because clouds do not block UV light.

Dr Guillon also recommends the frequent use of eyedrops to combat the dryness of alpine air, particularly for contact lens wearers.

?Don?t take your glasses off when you are sitting down to have a cup of coffee,? says Dr Guillon. ?You can damage your eyes sitting in an open-air caf? by the ski lift.?

A bout of snow blindness is painful, but it is unlikely to cause long-term damage. But skiers who repeatedly expose their eyes to UV light put themselves at risk of more serious problems, including macular degeneration and cataracts.

Need to know

• Striking back: Snow reflects (rather than absorbs) UV radiation. Depending on the age of the snow, around 50 to 85 per cent of UV radiation is reflected, which also puts areas such as the chin and nose tip at increased risk of sunburn.

• Peak hours: UV radiation is at its peak between 10 am and 3 pm. Don?t be fooled by cold and cloudy days ? you can still get sunburnt.

• Get snug: Aim for a snug fit, so that sunlight can?t shine over the top or sides of your eyewear. See your optometrist for more information.

• Clean up: Moisture, whether from snow or sweat, fog up goggles. Carry a tissue or a piece of cloth in your pocket to wipe it clean.