Smoke gets to your eyes

Smoking increases your risk of developing age-related macular degeneration, a condition that can cause narrowed vision and even blindness, according to a review of eye disease studies conducted on three continents.

"When the research was analysed, the question about smoking was kind of added to the research out of casual curiosity, but we were surprised to find that, in fact, people with a history of smoking are more likely to develop macular degeneration and to have a loss of vision from that than people who don't smoke," says Dr George Blankenship, president of the American Academy of Ophthalmology and a retinal specialist at Retina and Oculoplastics Consultants of Camp Hill in the USA.

Apart from age, in fact, tobacco smoking is the only risk factor consistently associated with any form of the disease, the study says. Details appear in a recent issue of Ophthalmology.

Age-related macular degeneration afflicts people mostly over the age of 60. Because it affects the central part of the retina, called the macula, it affects the centre of a person's vision - what you see straight ahead. Peripheral vision remains intact.

In more severe cases, daily activities like reading, driving a car, watching television, identifying currency and even recognising faces can become impossible.

But other than age-related macular degeneration, Blankenship says, smoking has not been linked to any other vision-related problems.

Precisely why smoking may contribute to the disorder remains unclear, he says.

"It's all speculation at this point, but we see two possible relationships," Blankenship says. "One is that we know that macular degeneration may have a vascular component, and people with a long history of smoking certainly have a higher risk of vascular disease, so there may be a connection there."

"In addition, we know that chemicals called free radicals can damage tissue, and smoking is believed to increase levels of free radicals, so that might also be an issue," he says.

Long-term smoking "probably increases the risk of people developing degeneration," he says, "and it probably accelerates the rate of deterioration for people who already have the condition."

According to Dr Jason Slakter, an ophthalmologist at the Manhattan Eye, Ear and Throat Hospital in New York, an additional factor may be the way the eyes appear to collect and store waste.

"There was some pathology work in England looking at various eyes that had been offered for research by deceased donors," Slakter says. "When they studied the tissue layer under the retina, which is directly responsible for regulating the activity in the macula, they found that those cells tended to concentrate all kinds of materials from cigarettes, including tar, and even little bits of plastic just from eating foods that may have been wrapped in plastic."

"So these cells really appear to scavenge a lot of waste products, and it could be that some of the tars or deposits from cigarettes actually poison or damage these cells directly," he says.

But regardless of the speculation about the actual process, Slakter says there's no question that smoking impacts the eyes.

"Of all the studies that have been done on macular degeneration, the single thing that has stood out is smoking, more than any risk factor," he says. "It's unbelievable."