Carrots help us to see in the dark. Our grandmothers have been telling us so for centuries. More contemporary dietary advice about eye health is that eating spinach and spring greens between two and four times a week may lower the risk of age-related blindness and developing cataracts, and that eating fish may relieve dry, gritty eyes.

Spinach and spring greens are especially rich in two yellow pigments called lutein and zeaxanthin, both capable of absorbing blue light. It is blue light in the sun’s rays that is most damaging to an area at the back of the eye called the macula, a supersensitive central region of the retina which, when damaged by exposure to sunlight, can result in macular degeneration.

The less serious dry form of age-related macular degeneration (which manifests itself from our fifties onwards) generally affects the ability to make out detailed, sharp images. If it progresses to the wet form, it takes away central vision: you cannot see what is directly in front of you.

About three million adults in Britain have some form of macular degeneration. Women seem to be more at risk than men because their eyes do not absorb lutein from their diets as efficiently as do men’s. People with blue eyes are more at risk because a light-coloured iris seems to allow more damaging light to penetrate to the back of the eye. Those with a family history of age-related blindness are also at greater risk.

One of the first scientists to observe the link between sight and eating these particular greens was Dr Johanna Seddon, of Harvard University, who published a paper in The Journal of the American Medical Association in 1994 showing that those who ate the most spinach and collard greens reduced the risk of macular degeneration by 43 per cent.

Since then a body of research confirming this link has beengrowingsteadily. Professor Ian Grierson, the head of ophthalmology at the University of Liverpool, explains: “In recent years more than 115 clinical trials and studies have illustrated that lutein, and its isomer zeaxanthin, can help supplement macular pigments in the eye which is otherwise being depleted through years of exposure to light and oxidative stress.”

We eat about 2mg of lutein a day in Britain. Dr Seddon’s research shows that when it is increased to 6mg daily, we appear to reduce the risk of developing macular degeneration by 57 per cent compared with those eating less than 1mg daily.

Kale is the best source of lutein, giving us a socking 22mg per 100g serving. But its strong flavour is not to everyone’s liking. Spinach, spring greens and water-cress are in second place with 13mg. Broccoli and peas give about 2mg per 100g serving, while red peppers have almost 14mg per 200g.

If none of these takes your fancy then try supplements. Taking 5mg of lutein twice a day has been shown to increase the pigmentation in the macula by 36 per cent within a year and it is thought that such intakes may even help to reverse some degeneration.

The idea that two pigments in vegetables act as internal sunglasses is something we should take seriously because as well as protecting against age-related blindness, they may make a difference to more subtle measures of vision.

For instance, as we age

our eyes become less sensitive to green and blue light and more sensitive to glare. Billy Hammond, a professor of vision science at the University of Georgia, sums it up: “Things like glare can kill you when you drive at night. Dense quantities of lutein and zeaxanthin in your macula can help ward off this problem.”

But eating for your eyes does not stop here. Dr Michel Guillon, a London-based optometrist and vision research scientist, explains how good nutrition affects eye health in other profound ways.

“Nutritional differences also appear to influence the risk of developing cataracts,” he says. Certain nutrients seem to help to reduce damage by the sun’s ultraviolet rays to proteins in the lens of our eyes. When damaged, the lens becomes characteristically cloudy.

“A high intake of DHA (docosahexaenoic acid, one of the essential fats in oily fish) and lycopene (the red pigment in tomatoes, watermelon and ruby grapefruit) is associated with a reduced risk of developing cataracts. In my view, supplementing with omega3 oils and lutein as well as lycopene, may reduce the risk.”

Guillon also promotes omega3 oils for people with dry eyes, a problem that especially affects women over 45.

And, of course, your grandmother was right — carrots really do help you to see in the dark. Their orange beta carotene pigment, also found in sweet potatoes, mangoes and apricots, helps our eyes to adapt to dim light. www.amandaursell.com

What else can help your sight?

— Wear sunglasses and a hat: amber lenses help to filter out blue light.

— Alcohol: men should avoid having more than six drinks a week and women three drinks, say US ophthalmologists, because alcohol lowers our levels of lutein and zeaxanthin.

— Cut down on processed foods: saturated and trans fats can cause hardening of the blood vessels, including those supplying oxygen and nutrients to our eyes.

— Exercise regularly: good circulation improves the chances of maintaining good sight.

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