Don't hang about with your eyes: get them tested by a qualified optometrist every couple of years. You might be suffering from macular disease, the most common cause of sight loss in the UK, and the early symptoms are not detectable by the sufferer themselves. The Macular Disease Society estimates that 513,000 Britons currently suffer from the condition, which affects a small area of the retina. It's about the size of a small grain of rice, but it nevertheless contains the greatest concentration of our photoreceptors.

There are two forms of the disease. One is called "dry" degeneration, which causes the macular region to wear out like a carpet. The photoreceptors die off, and affect a loss in vision. The second form is called "wet", and this refers to the growth of abnormal blood vessels within the macula. These bleed and leak fluid, which causes scarring of the macula, which in turn causes sight loss.

If wet macular disease goes untreated, people can lose their vision within a matter of weeks. But fortunately, this is the treatable form, and can be contained with regular injections into the eye of a drug called Lucentis. It sounds horrible, but in fact it's pretty painless.

There are also certain lifestyle choices you can make to protect yourself. If you don't smoke, you are four times less likely to develop macular disease than if you do. It's estimated there may be 40-50,000 people in this country who are sight-impaired because they smoke.

Second, it's thought that people who eat a diet low in antioxidants are more likely to develop macular disease. So eating lots of green, leafy vegetables like kale and spinach may help protect your macula.

Third, wet macular disease is associated with poor cardiovascular health. Taking exercise, keeping your weight down, and keeping your blood pressure down will therefore protect against the condition.

Last, if straight lines become wavy, or you develop blurred vision or lose patches of vision, that's a sign of wet macular disease, and you should go to your optometrist immediately.

There will be a lot of people for whom this advice will be too late. But there is a great support network available for them, not least from organisations such as the Macular Disease Society.

Cathy Yelf is a spokeswoman for the Macular Disease Society (maculardisease.org; 0845 241 2041). She was talking to Patrick Kingsley

• This article was amended on 19 April 2011. The original referred to the macular throughout. This has been corrected.