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There are more than two million people in the UK living with sight loss, according to the Royal National Institute of Blind People. Furthermore, the major causes of sight loss in adulthood include preventable conditions, such as age-related macular degeneration (AMD), إعتام عدسة العين, الجلوكوما and diabetic retinopathy.

Why should diet affect your eyes?

Parts of the eye, such as the retina and lens, are vulnerable to damage as we age. This is because the eye contains fatty substances, uses up lots of oxygen and is exposed to light for most of the day. These three things combine with our genetic profile to create the circumstances for oxidative damage - similar to when butter goes rancid when left in the sun.

Happily, a healthy diet contains plenty of antioxidants, nutrients which counteract oxidative damage in the body. Found in many different foods, such as colourful fruits and vegetables, tea, seafood and nuts, these balance out the negative effects of ageing in the eye.

Independent optometrist Francesca Marchetti says: "The antioxidants, lutein and zeaxanthin, are probably the most protective for the macula - that's the bit at the back of the eye that controls our detailed vision. If you lose function in that, it can be incredibly debilitating."

Body weight can also affect eye health. Excess weight (السمنة) often boosts inflammation and blood pressure, and increases your risk of داء السكري من النوع 2. All these conditions put stress on the eye. Diabetes can be particularly damaging, since raised blood sugars are harmful to the tiny blood vessels which bring much-needed oxygen and nutrients to the eye.

So, keeping your weight within a healthy range, by eating sensibly and minimising alcohol consumption, can help to protect your sight as well as supporting the heart and joints, and reducing your risk of certain cancers.

To find out which nutrients help to promote eye health and prevent AMD and cataract, US scientists ran a large clinical trial, called the Age-Related Eye Disease Study. This closely followed the progress of around 3,600 people with varying stages of AMD who were given a specialist dietary supplement, or a placebo (dummy pill), for several years.

The results showed that taking a high-dose dietary supplement reduced the risk of advanced AMD by 25% - which is a significant finding. The nutrients in the supplement included antioxidants, such as vitamin C, vitamin E and beta-carotene, and the minerals zinc and copper. Later in this study, lutein and zeaxanthin were added instead of beta-carotene and performed equally well.

In other research, vitamin E from both the diet and supplements was found to lower the risk of developing cataracts in older age by 27%, while higher intakes of omega-3 fatty acids (found in oily fish and fish oil supplements) were associated with a lower risk of AMD و dry eye disease.

These studies don't promise that diet is a cure for existing eye conditions but that it improves your chances of keeping your eyes in continuing health as you age. In addition, good nutrition and a healthier lifestyle can help stop early-stage problems, such as AMD and dry eye, getting worse. Next, we'll look at recommendations for healthy eyes.

Interestingly, a diet for eye health is similar to what you would eat to benefit other parts of the body. Marchetti says: "If you're eating healthily for heart and cognitive health, you're probably already looking after your eyes." She adds: "It's worth thinking about your eye health as early as your 30s or 40s, as that's when early abnormal changes can take place in your macula."

Marchetti's tips for eye health are:

Eat colour

Eat plenty of colourful fruits and vegetables which contain the antioxidant nutrients that boost eye health. These include kale, spinach, egg yolks, orange peppers, raspberries, blueberries, broccoli, kiwi fruit, squash, courgette, grapes and orange juice. Aim for at least five portions a day of fruits and vegetables, and a few eggs a week - these are no longer limited for people with raised cholesterol!

Think fish

Omega-3 fatty acids are important for eye health, especially helping to prevent dry eye which affects one in nine women aged over 40 years. Aim to eat oily fish (salmon, mackerel, herring, tuna) once a week, or take a daily fish oil supplement. White fish and seafood also contain zinc which helps to support your eyes so include a portion of these every week too.

Consider supplements

If you have a family history of AMD, it's worth taking a lutein and zeaxanthin supplement. This is because you would need to eat around 10 cups of kale or broccoli to get enough of these nutrients as you're already at risk of AMD.

Get tested

Have regular eye tests - these are about much more than glasses! Your optician is often the first person to spot changes in your eye health that could indicate a more serious condition, such as type 2 diabetes.

For more information on lifestyle tips and how to take care of your eyes, check out the College of Optometrists' الموقع الإلكتروني.