When Sarah, a 24-year-old from Hampshire, lost her sunglasses on the last day of a skiing holiday in the French resort of Alpe D’Huez, she did not bother to buy herself a new pair because it was an overcast day and she was going home in a few hours anyway. However, later that evening her eyes became uncomfortable and gritty, and by the next morning they were swollen and painful.
What Sarah had was a case of snow blindness, or photokeratitis, a form of sunburn of the cornea that may occur when the eye is exposed to excessive sun UV radiation, most commonly in latitudes closer to the equator, at high altitude or occasionally from the sea and sand glare.
Simon Kelly, consultant ophthalmic surgeon at the Royal Bolton Hospital, says painful, acute snow blindness resolves within a few days and, importantly, it can be prevented by wearing protective sunglasses.
But he warns of long-term damage to the eye from continuous exposure to bright sunlight over many years. “Research has shown that prolonged sunlight exposure is associated with an increased lifetime risk of developing cataracts, age-related macular degeneration (AMD), pterygium [a benign growth of the conjunctiva] and skin tumours around the eye,” says Mr Kelly.
He also points out that smoking, genetic predisposition, family history and diet play a significant part in causing cataract and AMD. “UV exposure may be a risk factor in the UK for people who work outdoors,” he says.
The Eyecare Trust, a charity that raises awareness of eyecare and eye health, advises that the risk of solar damage can be reduced by wearing sunglasses that provide adequate UV protection and a wide-brimmed or peaked hat that shades the eyes. Also, looking directly at the sun through binoculars or telescopes can damage the retina and may lead to sight loss, and children should be warned not to do this.
Long-term damage to the eye results from continuous exposure to bright sunlight over many years
Children are more vulnerable to the effects of sunlight because they have a clearer lens than adults, allowing up to 70 per cent more UV radiation to reach the retina. A survey by the College of Optometrists in 2009 found that 76 per cent of parents do not protect their children’s eyes in the sun.
However, there are different opinions of when children should wear sunglasses. Maggie Woodhouse, paediatric special needs optometrist at Cardiff University, says for most children, playing outside on a bright day in the UK, a hat that shades the eyes is sufficient protection. Dr Woodhouse suggests that most children only need to wear sunglasses when they are taken to exotic locations on holiday or at high altitude, for example when skiing, or playing on the beach or by water where there is a lot of reflected light.
With a view to buying the right sunglasses
Toy sunglasses or those not providing at least 99 per cent protection from UVA and UVB can actually cause more damage because the tinted lenses dilate the pupil, allowing more UV light to enter the eye, warns the Eyecare Trust.
Susan Blakeney, clinical adviser to the College of Optometrists, recommends always making sure sunglasses have the CE mark and are certified as complying with British Standards BSEN 1836:2005. This sets performance levels for quality, strength, stability, design and manufacture, as well as the amount of UV they let through.
Sunglasses also have a shade number relating to the tint of the lens, with 0 being the lightest shade and 4 the darkest. The colour of the lens does not a make a difference.
Dr Blakeney also warns that higher prices are not necessarily indicative of better quality lenses.
The Highway Code warns against very dark tints for driving and wearing tinted glasses at night or in poor visibility.
Contact lenses that react to sunlight are also starting to emerge on the market and the Eyecare Trust warns to only purchase these from a reputable seller.