Smoking Heightens Chance of Blindness, Medical Study Says

People who smoke a pack of cigarettes a day double their likelihood of developing the most common cause of blindness among older Americans, according to two new studies in today’s Journal of the American Medical Assn.

The more people smoke and the longer they smoke, the higher their risk of developing the usually untreatable malady, age-related macular degeneration, the research found. Years after quitting, former smokers still faced up to double the risk of getting the condition, which impairs the vision of an estimated 1.7 million Americans, government statistics show.

“It is another reason to either not smoke, quit smoking or reduce your amount of smoking,” said Dr. Johanna M. Seddon of the Massachusetts Eye and Ear Infirmary and Harvard Medical School.

In advanced macular degeneration, which affects one of every 14 people age 75 or older, the center of the visual field deteriorates, causing a roughly circular area of blindness that gradually grows.

The deterioration is caused by damage to the macula, the center of the retina, a light-sensitive membrane on the inside back of the eyeball. The damage occurs when an insulating layer between the retina and blood vessels that nourish it breaks down, resulting in fluid leaks and scarring.

Smoking may speed the process by increasing the number of damaging chemical compounds or reducing the number of protective nutrients delivered by the bloodstream to the eye, researchers speculate. Another theory is that smoking reduces blood and oxygen to the eye.

Seddon led researchers who looked for macular degeneration among 31,843 initially healthy women during a 12-year period beginning in 1980 in the ongoing Nurses’ Health Study. In 215 cases that developed, the disease caused vision loss; almost one-third of those cases were attributable to smoking, researchers said.

Smokers of a pack of cigarettes or more a day were 2.4 times as likely to develop macular degeneration as women who had never smoked. Risk was calculated after controlling for differences in other traits that can be important, such as age, diet and estrogen use.

Dr. William G. Christen of Harvard-affiliated Brigham and Women’s Hospital led a team that looked for macular degeneration among 21,157 initially healthy men during an average 12-year period beginning in 1982 in the ongoing Physicians’ Health Study.

Among the men, macular degeneration developed in 268 cases, causing vision loss. Christen’s team did not calculate how many cases were attributable to smoking, but he said it would be comparable to the proportion among women.