12
Freeman, Cataract Surgery and Age-Related Macular Degeneration
greater progression of early AMD (OR=2.0, 95% CI 1.3-3.0)
8
, but not with the incidence of
early AMD.
There are several possible reasons that might explain, either individually or in concert,
the association between cataract surgery and late AMD that we, and others, have observed. One
possibility is that cataract and AMD simply share one or more common risk factors. In our
analyses, the finding that severe cataract was also associated with a modestly increased
prevalence of late AMD indicates that it may not be the cataract surgery but perhaps factors
leading to cataract that potentially have a causal relationship with late AMD. The association
between cataract surgery and late AMD persists after controlling for the known common risk
factors of age and smoking. However, there may be other risk factors (environmental or genetic)
that have not been identified, or cataract and late AMD may both be markers for accelerated
aging.
A second possibility that could explain the association between cataract surgery and
AMD is that we are less likely to detect late AMD in those who may still have a lens opacity in
the eye. However, this should not be an issue in our study because those with severe cataract are
not included in the reference population. Therefore, there should not have been a problem in
detecting retinal pathology in the reference population. Likewise, an ophthalmologist may look
more carefully for signs of AMD in an eye that has had cataract surgery in the past. However,
retinal photographs were used for two of the studies and the graders had no knowledge of
whether the person had cataract surgery or not.
A third possibility is that cataract surgery in some way physically predisposes an eye to
develop AMD, perhaps through inflammatory mechanisms
12
. The epidemiological data cannot
directly address this possibility. Our data indicate that the prevalence of late AMD does not
