EYESIGHT is perhaps the most vital of the six senses, yet the biggest risk to our sight as we age is a relatively unheard of complaint.

Macular disease is the leading cause of vision loss in people over the age of 65.

Macular degeneration affects over 500,000 people in the UK and is the largest cause of people being registered as visually impaired, yet most of us have never heard of it.

The disease is a progressive condition which causes changes in the tissues of the eye. The macula is located at the back of the eye at the centre of the retina.

It allows the eyes to see fine detail and objects directly in front of the field of vision.

It plays a vital role in helping people to read, write, drive and perform other detailed tasks. It also enables us to recognise faces and see colour.

Sheila Childs, 63, from Thundersley, was diagnosed with macular disturbance three years ago after experiencing problems with her right eye.

"At first I just had a headache and thought I had overdone it," she explains, "but then the vision in my eye began to alter."

Sheila went straight to her optician and was told that she had leakage from her macular into her retina.

"It is hard to describe what it is like," she says "I have like a yellow spot in the centre of my vision.

"The best way to describe it is that the centre of the vision is blurred, but the outer edges of my vision are clear. It is like looking through a mist in the centre."

Although Sheila's eye managed to heal itself, the leakage happened again last year and again her vision was affected in the same way.

She was told she could have laser surgery to seal the leak, but that it would leave a scar on her eye and she is uncertain whether to go ahead.

In the meantime she has to monitor her eyesight as if left unchecked she could go blind.

Sheila explains: "I have a grid I have to look at once a week and when the lines become more distorted I know it is time to get it checked.

"I have also been told that diet can help and that I should try to eat lots of dark leafy greens like spinach, sweetcorn and tomatoes as these all contain essential nutrients."

There is no cure for macular disease, although some research has shown that high doses of beta-carotene, vitamins C and E, and zinc may help to slow down the deterioration.

Experts are still unsure as to what causes the disease, but it becomes more likely as a person ages because, over time, the cells in the macula become damaged and worn out.

There are two main types of the disease - dry and wet.

Dry is the most common form of the condition.

Cells in the retina fail to function properly as a person gets older. The cells don't take in enough vital nutrients and fail to clear by-products of cell functioning.

This causes tiny abnormal deposits, called drusen, that are left under the retina, making it uneven.

In time, the cells degenerate and die causing sight loss, but it is often hard to diagnose as this occurs very gradually over many years.

Wet macular disease accounts for 10 to 15 per cent of cases. It often develops quickly because it involves the growth of new blood vessels behind the retina.

These new blood vessels are very fragile and so may leak fluid or blood. This results in scarring that causes rapid loss of vision.

For Harold White, 83, of Basildon, the deterioration caused by macular degeneration went unnoticed for many months. His daughter Linda Stevens explained: "Because only the right eye was affected at first the other eye compensated, but then six months ago he felt something in the left eye and so went to see a specialist."

Harold was diagnosed with age-related macular degeneration, something neither had ever heard of before.

He must now have regular injections in his eye to help slow the degeneration and preserve his sight.

Linda said: "It was only when I read an article that I understood how common it was. The secret is to catch it early and get it checked out. Eyes are very precious so any change should be investigated."