Thanks to years of public health warnings and campaigns, most of us are well aware of the dangers of over-exposing the skin on our face and body to the sun. We have learned to take precautions to protect ourselves, such as using sun cream and avoiding mid-day sunlight, to avoid developing health problems such as skin cancer. Unfortunately, it is not so well known that the sun’s rays can not only make us squint, leading to ageing wrinkles and lines, but can cause extreme medical damage to our eyes. These problems can be avoided by wearing the right sunglasses for UV protection.
Cancer of the eyelid
Like skin in other parts of the face, the skin on the eyelids can develop melanomas, basal cell carcinomas and squamous cell carcinomas. The eyelid is an area where between 5 to 10 per cent of all skin cancers are found. Sunblock cream cannot easily be applied to the eyelids and sunglasses are the best form of protection for this delicate area.
This is the most common form of eye cancer found in adults. Cancerous cells develop in the uveal tract; the middle layer of the wall of the eye that includes the iris, the ciliary body and the choroid. These often go undetected, as they lie in an area that is not easily visible and are likely to spread to other areas of the body. The first sign of intraocular cancer is usually a blurring of the vision. The conjunctiva, the protective membrane that covers the eyeball and the inside of the eyelids, is prone to benign and malignant growths as well.
Cataracts are the main cause of blindness in the world and the most common cause of vision loss for those over 40. They cause a clouding of the eye’s natural lens. There are several types of cataract caused by many different risk factors. One of the main risk factors includes ultraviolet radiation from the sun.
Damage to the retina that builds up over time is age-related, but this degeneration is more likely in those who have had unprotected exposure to large amounts of bright sunlight when they were younger. Several studies have found that those who spent a significant amount of time in the sun in their teens, twenties and thirties were twice as likely to develop AMD in later life.
If the surface of the eyeball is exposed to strong sunlight for long periods without protection by sunglasses, it is possible for the cornea to suffer from radiation damage and sunburn of the cornea. This is the area of the eye that absorbs most UV radiation and damage is usually cumulative, although it can be triggered by exposure to reflection from snow fields at high elevation.
It is therefore extremely important to protect this sensitive area of the body from damage by the sun’s rays. We should make it a daily habit to wear sunglasses whenever we are outside, as UV radiation can penetrate the eyes even on cloudy days.
They should block out light
Sunglasses should obviously not block out all light reaching the eyes, but they need to screen out at least 75%-80% of light to be effective. To see if a pair is dark enough, try them on in front of a mirror. You should not be able to easily see your eyes when wearing them; if you can, the lenses are too light. The darkness of the lenses do not always indicate their effectiveness, though; mirrored lenses will eliminate glare but they will not block out harmful rays unless they are clearly marked as giving full UV protection.
They should provide complete UVA/UVB protection
Not all sunglasses block out UVB and UVA rays, even if the lenses are dark. It is vital to choose a pair that are labelled as blocking out 99% to 100% of UV rays. Ideally, they should offer UV 400 protection; this shields the eyes from even the very smallest of UV rays with a wavelength of up to 400 nanometers. Choose sunglasses that are labelled as meeting the American National Standards Institute ANSI Z80.3, or that have a CE mark showing that they meet European safety standards. Never pick a pair that does not provide any details of UV protection.
Check for quality
While buying an expensive pair of glasses does not guarantee quality, cheaper models can be shoddily manufactured so it pays to check them thoroughly before buying. Look closely at the lenses to see that the tint is uniform over the whole surface with no areas that are darker than others. Check for imperfections by focusing on a straight line, such as a doorframe or mirror’s edge. Move your head slowly and let your eyes move slowly too, to see if line curves or distorts; if it does, do not choose those sunglasses.
Pick polarised lenses for some situations
Polarised lenses are ideal for those spending time by the sea or on the water as they filter out reflected sunlight that bounces off water and they will also filter out bright sunlight that reflects from snow. Sunlight also bounces off smooth surfaces such as pavements and roads, making polarised lenses a good choice for drivers. Polarisation alone does not protect from UV rays, though, so check that polarised lens include UV protection.
Choose wraparound frames and larger lenses
Fashion sunglasses often have small, ‘John Lennon-type' circular lenses or are made in quirky, retro designs in unusual shapes such as hearts or flowers. These do not protect the eyes from peripheral glare and it is better to choose wraparound frames for sunglasses. If these are not acceptable, a second-best choice is large lenses that reach to the cheekbones with side-frames that have wide temples. These will protect the eyes from every angle as sunlight can hit the eyes from the sides and above as well as directly in front.
Make sure that they fit properly
Sunglasses that are perched on the nose or that slip loosely from the ears will expose the eyes to UV rays coming in from above and from the sides. Frames should fit snugly on the nose and ears so that the lenses completely cover the eye socket, without pinching or rubbing.
While all these factors will help you choose the very best sunglasses, remember that nothing will protect your eyes from certain intense light sources. Do not gaze directly at an eclipse, at arc welding or at tanning lights even when wearing sunglasses and wear specialised goggles if you are spending time in large snowfields.