BEIJING, July 12 -- A recent study shows that smoking increases the chances of developing age-related macular degeneration (AMD), a main cause of blindness among the elderly.

In a study of male twins, researchers have found cigarette smoking increased the risk of the AMD, most common cause of blindness among the elderly.

    According to the study conducted by researchers at the Massachusetts Eye and Ear Infirmary in Boston, smokers were twice as likely to develop macular degeneration than those who had never smoked. People who quit smoking had a risk lower than smokers but more than those who never became addicted to tobacco products.

    The study team studied data from 681 individual male twins in their mid-70s who were World War II veterans.

    All participants were given eye examinations and had their height, weight and blood pressure measured. They filled out questionnaires about their diets and whether or not they smoked. The scientists factored in other risk factors, such as any prior diagnosis of AMD.

    The researchers found:

    --222 had intermediate and/or late-stage AMD.

    --459 had no signs of AMD at all.

    --Those who were still smokers were 1.9 times more likely to have AMD.

    --Those who used to smoke were 1.7 times more likely to have AMD.

    Study leader Dr. Johanna Seddon stated that eating a healthy diet, doing regular exercise, not smoking and maintaining a normal healthy weight helped protect people from developing AMD.

    Most experts agree that AMD risk is largely dependent on your genes. However, your lifestyle can have an enormous impact on when you develop it, according to Seddon.

    The results of the study were published Monday in the journal "Archives of Ophthalmology."