People who smoke have double the risk of suffering from a degenerative eye disorder that is the leading cause of Blindness in the elderly, researchers said on Thursday.

A study of more than 4,000 Britons aged 75 years and older showed that those who smoke were twice as likely to have age related macular degeneration (AMD) as those who didn’t.

“Smoking is associated with a twofold increased risk of developing AMD,” said Professor Astrid Fletcher, of the London School of Hygiene and Tropical Medicine, in a study published in the British Journal of Ophthalmology.

AMD is an illness that blurs the central vision. It affects the macula, or part of the eye that sees fine detail. In the United States alone it afflicts about 10 million to 15 million people.

The risk of suffering from the illness increases with age.

Fletcher and her colleagues questioned people in the study about their smoking habits, alcohol consumption and cardiovascular disease.

People who had stopped smoking more than 20 years earlier had no increased risk developing the illness. Based on the findings, the researchers estimate that smoking is likely to have been linked to up to 30,000 cases of the disease in Britain.

“An increased risk of AMD, which is the most commonly occurring cause of Blindness in the United Kingdom, is yet another reason for people to stop smoking and governments to develop public health campaigns against this hazard,” Fletcher added in the study.