New research gives smokers one more reason to quit: pack-a-day-or-more puffers double their likelihood of developing the most common form of blindness among the elderly. The more people smoke and the longer they smoke, the higher the risk of developing macular degeneration, according to two studies in the October 9, 1996 issue of The Journal of the American Medical Association.
In advanced macular degeneration, which affects 1 of every 14 people aged 75 or older, the center of the visual field deteriorates, causing a roughly circular area of blindness. The deterioration is caused by damage to the macula – a light sensitive membrane at the center of the retina. The damage occurs when an insulating layer between the retina and the blood vessels that nourish it breaks down resulting in fluid leaks and scarring.
Smoking may speed this deterioration 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.
According to a report in the British Medical Journal from public health experts at the University of Manchester, smokers are up to four times more likely than non-smokers to develop age-related macular degeneration (AMD). In Britain an estimated 53,900 persons over the age of 69 have AMD attributed to smoking. 17,900 of them are legally blind. Smoking can also affect the outcome of photodynamic therapy and other laser therapies to treat macular degeneration.
The causal association between smoking and AMD is biologically plausible. Smoking is known to impede the effects of antioxidants and to reduce macular pigment density. Oxidants can damage the retina.
Observational studies showed that former smokers have only a slightly increased risk of developing AMD compared with those who have never smoked. Cessation of smoking has important implications for people with macular degeneration in one eye and not the other.
Many health professionals are now calling for the risk of blindness to be included in the litany of smoking-related illnesses. Quitting smoking is the one prevention method known to reduce the risk of developing AMD. In New Zealand and Australia, publicity relating smoking and blindness brought more telephone calls to the national Quitline than did other advertisements relating smoking to stroke and heart disease.