Eye care in the sun
Summer is here and you will be spending a lot more time outdoors. Most likely you will be protecting your skin with sun-block and appropriate clothes, but what will you be doing for your eyes?
In a similar way to sunburn, UV radiation causes damage to the outer surface of the eye (called the cornea) and also the internal parts of the eye that are necessary for sight. Short-term UV exposure usually causes only minor eye irritations, but long-term UV exposure can lead to permanent damage to the eyes and decreased vision or blindness.
Sun in your eyes
Conditions caused by long-term sun exposure include:
- Sunburn of the cornea
- Pterygium (pronounced tur-rig-i-um), an overgrowth of the conjunctiva on to the cornea.
- Cataract, or cloudiness of the cornea.
- Cancer of the conjunctiva (thin membrane covering the eye).
- Skin cancers on the eyelids and around the eyes.
- Life-long sun exposure is also thought to be a factor in the development of macular degeneration (the macular is part of the membrane at the back of the eye which picks up light, turning it into a visual image).
A cataract is a clouding of the lens of the eye which blocks the entry of light into the eye, leading to reduced vision, and if left untreated can lead to blindness. It is primarily caused by the ageing process. The number of Australians with a cataract will increase by 65 per cent over the next 20 years to an estimated 2.7 million by 2021. Cataracts are caused by a gradual increase in oxidative damage to the eyes that is part of the normal ageing process. However, they are also caused by exposure to oxidative chemicals such as those found in cigarette smoke and by long-term exposure to UVB radiation. It has been estimated that 10 per cent of cataracts seen in Australia are due to UVB radiation exposure to the eyes.
Antioxidant vitamins that slow the normal ageing process and protect the eyes from the harmful effects of UV radiation, such as vitamin E, selenium and beta-carotene, have been found to be low in people who have cataracts. It has also been shown that people who eat the recommended amounts of antioxidant-rich fruit and vegetables have a lower incidence of cataracts compared to people who do not eat enough fruit and vegetables.
Macular degeneration is the leading cause of blindness in Australia and affects one in seven Australians over the age of 50. It is caused by the thinning of and damage to the central point (the macular) of the light-sensitive membrane (the retina) at the back of the eye. It leads to reduced vision of fine detail and black or missing spots in the centre of the field of vision and can eventually cause blindness. It is primarily seen in older persons but it can sometimes occur in younger people. Smokers are at a much higher risk than non-smokers.
Dietary intake of antioxidants — particularly the red, orange and yellow plant pigments known as carotenoids found in fruits and vegetables — have a protective effect on this delicate area of the eye. The body accumulates these carotenoids in such high concentrations in the eye that the macular is actually bright yellow in colour. Damage caused by oxidative substances, such as cigarette smoke, UV radiation and pollution, is thought to be a major factor in the development of macular degeneration.
Pterygium is a common eye complaint in which the membrane of the white part of the eye grows over the cornea. It can look unpleasant and become irritated and red, but it can also affect your vision if the pterygium grows over the pupil and blocks the passage of light into the eye. The incidence of pterygium is much higher in people who have had a life-long exposure to high amounts of UV radiation, such as farmers and surfers. It has been estimated that almost half of the 8600 cases of pterygium treated annually in Australia, for example, are caused by UV exposure.
Effects of UV radiation
(3 columns 2 rows) Type of UV Health effects UVA Not needed for vision Premature ageing Skin wrinkling around the eyes Implicated in skin cancer UVB Not needed for vision Cancer on the eyes, eyelids and skin around the eyes Damage to the cornea, lens and macular Cataracts Sunburn
Levels of UV radiation are particularly high in the summer months between the hours of 10am and 3pm. People who spend a lot of time outside during these times are most at risk of UV damage to their eyes. Research has shown that people with fairer skin and light-coloured eyes are more prone to eye problems caused by UV damage than those with darker complexions.
Staying in the shade during the hottest times of the day and wearing UV-absorbing sunglasses are the best ways to reduce the risk of UV damage to your eyes. Even when you are in the shade it is still important to wear sunglasses to protect your eyes, as UV radiation can be reflected off surrounding surfaces such as water, sand, concrete, car windshields and even the moisture in the air.
Researchers have found that levels of UV radiation in the shade can reach levels high enough to cause damage to your skin and eyes, even in the winter.
Choosing your sunglasses
Many people view sunglasses simply as a fashion accessory, but they are the best way to reduce UV damage to your eyes. Expensive designer sunglasses are often made with higher-quality lenses and frames and may therefore last longer, but don’t be fooled into thinking that a higher price will buy you superior eye protection. Regardless of the cost of the glasses, it is the shape and the UV absorbency of the lenses that determines the level of protection they provide.
For the best protection you should choose a pair of sunglasses labelled as having an eye protection factor of “EPF10”, or “UV400” (meaning the lenses block 100 per cent of UV), which indicates that the sunglasses have met the Australian and New Zealand standard for sunglasses.
The shape of the sunglasses is also very important, as UV radiation can enter the space between your eyes and the lenses and be reflected back into your eyes, increasing the risk of damage. Choosing a pair of sunglasses that wraps around your face and has close-fitting frames will reduce the risk of this happening.
The darkness of lenses does not give any indication of how much UV protection the sunglasses offer. It’s always important to check the label. The colour of the lenses determines what other types of light are filtered out, such as reflected blue or white light, making some coloured lenses more suitable for certain sports or weather conditions.
Most lenses are grey/black coloured, but there are also many other lens colours available such as brown/amber, yellow, rose and blue. Polarised lenses reduce glare and may be helpful when driving for long periods but they do not offer any additional UV protection.
On the inside
Exposure to UV radiation creates reactive substances on the surface of the eye known as free radicals, which damage the eye and deplete the antioxidants found in the tissues and fluids in and around the eye.
The free radicals created from UV exposure are believed to play a significant role in the development of several eye conditions including cancer of the cornea, cataract, pterygium and macular degeneration. The antioxidants found in the eye include those from dietary sources such as vitamins A, C and E, carotenoids such as beta-carotene and lutein and several antioxidant enzymes produced by the body itself.
A constant, adequate supply of dietary antioxidants is required to maintain the antioxidant protection of the eye. If there are inadequate levels of antioxidants in the eye, UV radiation is more likely to cause damage to the eye surface and also allow more UV radiation to penetrate deeper to the delicate areas at the back of the eye.
Pigments for protection
One of the main groups of dietary antioxidants that provide UV protection for the eye is the carotenoids, a group of yellow, orange and red plant pigments found in fruits and vegetables. Some carotenoids are converted in your body to vitamin A, which is used by the light-sensitive cells in the eye to produce vision and is essential for the division and growth of all the cells in your body.
Carotenoids also act as antioxidants in the body where they are involved with DNA repair, neutralising free radicals, cancer prevention and aiding the effective function of the immune system. Eat foods of the following colours to ensure you are getting your protective carotenoids.
Betacarotene is the best-known carotenoid and is found in abundance in orange-coloured fruits and vegetables such as carrots, rockmelon, pumpkin and also dark green leafy vegetables such as spinach. It is often found in supplements in the form of freeze-dried orange algae called Dunaliella salina, which contains large amounts of betacarotene.
Lutein and zeaxanthin are necessary for the protection of your eyes from the harmful effects of UV radiation. Some specialists consider these carotenoids essential nutrients as a low dietary intake of lutein and zeaxanthin is linked to a considerable increase in the risk of macular degeneration.
Lutein is found predominantly in yellow foods such as corn and yellow capsicum but also in dark green leafy vegetables such as spinach and kale. Zeaxanthin is found in orange foods such as orange capsicum, persimmons, mandarins, oranges, paw-paw and dark green leafy vegetables.
The yellow colour of lutein is due to the fact that it absorbs UV radiation and blue light, which has the most damaging effects on the structures of the eyes. It is the ability to filter out UV combined with the ability to mop up any free radicals produced by the UV radiation that makes lutein so special.
Lycopene is a red-coloured carotenoid that has recently been popularised for its cancer-preventing effects on the prostate. Its antioxidant effects are not confined to the prostate, however — it is also very effective at reducing the damage to the eye caused by UV radiation and offers a protective effect against many types of cancer. It is primarily found in tomatoes but also in guava, pink grapefruit, watermelon and papaya.
Astaxanthin is a pink-coloured carotenoid responsible for the vibrant colour of salmon, lobster, prawns (and also flamingos). It is found in large amounts in algae and small sea creatures, which these animals all eat in the wild; however, in farmed seafood such as prawns and salmon, a synthetic form of astaxanthin is added to their feed to give their flesh the desired colour.
Astaxanthin is a powerful antioxidant that has been found to effectively reduce the damage caused by UV radiation and is often promoted in supplements as an “internal sunscreen”. Some research has found that astaxanthin may have a higher antioxidant activity than other carotenoids including betacarotene, lycopene and lutein.
While there may be benefits from supplementing astaxanthin in people who spend a great deal of time in the sun and are concerned about UV damage to their eyes, it does not reduce the need for adequate external sun protection such as high-protection sunscreen and sunglasses.
Eat a rainbow
We are only just beginning to understand the potential benefits to eye health offered by carotenoids in the diet. Research has demonstrated that a diet low in these nutrients significantly increases the risk of many different eye problems. However, studies that supplement large doses of single antioxidant nutrients have yielded mixed results and in some cases may cause additional damage or health problems.
The best way to minimise the harmful effects UV radiation has on your eyes is to always wear adequate UV absorbing sunglasses when outside in the middle of the day and eat a balanced diet rich in a wide variety of high antioxidant fruit and vegetables. By eating a broad mix of coloured fruit and vegetables each day, you can ensure you are giving your body an adequate supply of UV-protecting antioxidant plant pigments to prevent eye problems and maintain good vision.
Nutrients for UV protection and eye health
Converted into vitamin A in your body, immune regulating, acts as an antioxidant to protect your skin and eyes from the damage caused by free radicals.
Carrots, rockmelon, pumpkin, sweet potatoes, dark leafy green vegetables.
Anti-cancer, immune enhancing.
Tomatoes, guava, watermelon, pink grapefruit.
Protects your eyes from the damage caused by UVB radiation.
Corn, yellow capsicum, marigold flowers, dark green leafy vegetables.
Protects your eyes from the damage caused by UVB radiation.
Orange capsicum, persimmon, mandarins, oranges, paw-paw, marigold flowers, dark green leafy vegetables.
Powerful antioxidant, protects your skin and eyes from the effects of UV radiation.
Fat soluble antioxidant that reduces the effects of ageing and improves heart health.
Avocado, wheat germ oil, almonds, sunflower seeds, hazel nuts, pinenuts.
Protects the cornea from damage caused by free radicals.
Oranges, guava, capsicum, kiwi, grapefruit, strawberries.
Anticancer, antioxidant, recycles vitamin C and E.
Brazil nuts, brewer’s yeast.