A study pooling results from several population-based eye disease studies conducted on three continents shows that tobacco smoking is the principal known preventable risk factor associated with age-related macular degeneration (AMD). The study appears in the April 2001 issue of Ophthalmology, the clinical journal of the American Academy of Ophthalmology, the Eye M.D. Association.
The study, analyzing combined data from studies conducted in Beaver Dam,
Wisconsin, Rotterdam, the Netherlands, and the Blue Mountains area, west of
Sydney, Australia, shows that apart from age, tobacco smoking is the only risk
factor consistently associated with any form of AMD in each study location and
The two forms of AMD are geographic atrophy (or dry AMD), and neovascular
(or wet AMD). In dry AMD, the retina thins out gradually. There is no known
cure for this type. In wet AMD, new blood vessels in the retina grow and leak
blood or fluid, damaging the macula, the part of the retina responsible for
central, focused vision. The two treatments currently available for this type
of AMD are laser photocoagulation and photodynamic therapy, both of which can
stabilize the disease if caught early enough. Compared with people who never
smoked, ex-smokers and current smokers were more likely to have AMD. Current
smokers were more likely to have wet AMD than dry AMD.
Academy spokesperson Paul Sternberg, Jr., M.D., said, "This study
corroborates and reinforces previous studies that have suggested the link
between tobacco smoking and the development of macular degeneration. The
Academy supports the authors' call for increased health advocacy efforts to
reduce the smoking rate, including among the elderly."
Interestingly, even though both the Beaver Dam and Blue Mountains eye
studies showed the prevalence of wet AMD to be twice that of dry AMD among the
study participants (ages 55 to 86), the ratio was smaller in the Rotterdam
study. The authors discuss several possible explanations for this difference
-- such as differences in retinal photographic technique, patient selection,
health care systems, cultural attitudes about health, exposure to sunlight,
and environmental risk factors. However, they rule these out as likely
explanations, suggesting that there may be important genetic differences and
gene-environment interactions among the three communities, and they call for
more research to identify genes that may predispose people to developing AMD.