The eye is one of the most astonishing organs in the body, working constantly to turn light into streams of nerve impulses which the brain can convert into visual images.

But although our vision dominates how we understand the world around us, most people take it for granted, giving little thought to the complex processes that enable them to see, until one day they realise they have a problem. From midlife onwards several different eye conditions become common and by the age of 45 most people have noticed that they can’t see as well as they once could. Some of these problems can be corrected with glasses or contact lenses while others need medical treatment or surgery. But there is plenty that you can do yourself to keep your eyes healthy and delay the changes associated with aging.

A diet rich in anti-oxidants will help to combat the ravages of time and environmental pollutants. This means plenty of vitamins A, C and E and carotenoids (good sources include red, orange and yellow vegetables and fruit). Selenium is also important (found in liver, kidneys and seafood. In the UK soil levels of selenium are low and vegetables are rarely a good source.) Another group of chemicals, called flavonoids also has powerful antioxidant effects. They are found in fruit, vegetables, pulses, wine and tea (especially green tea).

It’s essential to have eye tests regularly. Many diseases can be only detected by careful testing or a thorough examination of the inside of the eye, especially during their early stages. Deal promptly with any sudden eye problems or trauma. In bright sunshine, always wear sunglasses to protect your eyes from high doses of ultraviolet light which can speed up age-related changes in vision and avoid eye-strain by limiting the amount of time you spend in front of a computer screen.

Time for reading glasses?
Even if you do everything you can to look after your eyes, you may start to find that it becomes more difficult to focus clearly on objects held close to you. This problem, called presbyopia, usually starts at about 40-45 and is so common that it is regarded as a normal change of aging. It is caused by changes in the lens inside the eye, which becomes larger and stiffer and less easily changes its shape (or ‘accommodates’) to focus light coming from objects close to the eye. Most people first notice that reading becomes more difficult, especially in low light. Glasses or contact lenses for short or long sightedness don’t help presbyopia, and can even make it worse. Neither can surgery help. The only answer is to wear special reading glasses, or change to bifocal lenses.

Age-related macular degeneration
AMD affects nearly 1 in 10 people over 40, and is the most common cause of blindness in the developed world. In this painless condition, the macula, or central part of the retina (the light-receiving membrane at the back of the eye) becomes damaged due to the irreversible death of light-receptor cells or the invasion of leaky, unwanted blood vessels into the retina. The result is blurred central vision which interferes with activities such as reading or driving.

Once the condition has reached an advanced stage, there is no effective treatment but research has shown that people whose diet is rich in green leafy vegetables have a lower risk of developing AMD and nutrition may help to prevent progression. In the USA the National Eye Institute’s Age-Related Eye Disease Study (AREDS) found that a high-dose formulation of antioxidants and zinc significantly reduced the risk of advanced AMD, although it could not cure the disease or restore lost vision. This formulation included 500mg of vitamin C, 400iu vitamin E, 15mg beta-carotene (equivalent to 25,000iu vitamin A), and 80mg zinc. These high levels of nutrients are difficult to achieve from diet alone so researchers now recommend that anyone at risk of advanced AMD should consider taking supplements.

More recently studies have shown that two particular antioxidant carotenoids called zeaxanthin and lutein are found in very high concentration in the macula and help to keep it healthy. Some people such as smokers who are at increased risk of AMD have low levels of zeaxanthin and lutein in the macula, while people with high levels in their diet appear to have less damage to the eye and a reduced risk for advanced AMD. Spinach and greens are a particularly good source of zeaxanthin and lutein, but supplements may be a more reliable way to ensure you get enough.

Cataracts, glaucoma and diabetes
Micronutrients may also be important in reducing the risk of cataracts, which are cloudy areas in the lens. Cataracts are very common - in fact most people develop some clouding of the lens after the age of 60 and by 75, 70% have visually significant cataracts. Once formed, they must be surgically removed. Factors that may contribute to cataract development are low calcium levels in the blood, diabetes, excessive exposure to ultraviolet light (sunlight) and smoking. So simple steps such as wearing sunglasses and giving up smoking can reduce the risk. The nucleus of the lens is particularly sensitive to nutrient deficiencies. Research has shown that vitamin A and B types such as niacin, thiamin and riboflavin may protect against cataracts, while other studies have linked high zeaxanthin and lutein consumption with a lower risk.

About one in 90 people suffers from glaucoma, a condition where the pressure inside the eye rises, damaging the optic nerve. This causes visual loss which can develop very gradually and go unnoticed until permanent damage has been done. It’s very important to be tested regularly for glaucoma, particularly when others in your family have had the condition. Medication or surgery can reduce the pressure. In some people with glaucoma, magnesium has been shown to help improve vision slightly by improving blood flow. Although this early research may be relevant only to a small proportion of people and is no substitute for proper medical treatment, people at risk of glaucoma may want to make sure that their diet is rich in magnesium (from whole grains, nuts, green veg etc).

People with diabetes are particularly vulnerable to glaucoma, cataracts and many other eye problems, which may develop even before the diabetes has been diagnosed. Those at risk for diabetes, perhaps because of a strong family history, should be vigilant for problems and people should have their eyes tested at least once a year.

Future improvements
Laser therapy has already meant that hundreds of thousands of people have been able to throw away their glasses, although it is expensive and still carries a significant rate of complications. In the future new technology and treatments such as gene therapy may lead to much greater improvements, and even cure, of many common eye problems. But for now at least we all need to do everything we can to look after our eyes.

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