28
further study, in order to better characterize it, to
determine its causes and to identify strategies to limit
this potentially deleterious effect.
In conclusion, AMD is emerging as a disease resulting
from major genetic susceptibility, the effect of which is
modulated by lifestyle. Among lifestyle factors, smoking
is the best characterized risk factor, now considered as
causal, while the role of nutrition is increasingly iden-
tified. The respective roles of antioxidants, macular
pigment and omega 3 fatty acids, together with other
potential nutritional factors such as vitamins B and D,
will be better understood in the future. In this field, sev-
eral new epidemiological studies are being conducted,
among which, in France, the Alienor Study
(85)
. This
population-based cohort study aims at assessing the asso-
ciation of AMD with nutritional, vascular and genetic
risk factors. It bears on almost 1000 subjects, recruited
from an existing cohort study on brain ageing (the 3C
Study). The main nutritional factors studied are lutein
and zeaxanthin, antioxidants (vitamins C, E, zinc) and
omega 3 fatty acids, and are measured both in the diet,
in plasma and, for lutein and zeaxanthin, on the retina.
This study will add to the existing literature in this field,
which is still relatively scarce and partially inconsistent.
Moreover, several large controlled interventional trials,
including the AREDS2 Study, will help demonstrating
their causal role in the aetiology of AMD. Finally, the
role of light exposure (in particular blue light) does not
seem to be major determinant in this disease, but may be
important in subgroups of the population (subjects with
low antioxidant and macular pigment intake, subjects
undergoing cataract surgery).
AMD is at most modest. Interestingly, a recent study
evidenced an association of the risk for AMD with blue
light exposure, only in those subjects with low plasma
antioxidants and zeaxanthin
(27)
. This suggests that light
exposure may increase the risk for AMD only when
defences against the produced reactive oxygen species
are not appropriate. Sunlight exposure therefore does
not appear to be a major determinant of AMD, but may
be a risk factor in susceptible individuals. Appropriate
nutritional intake in antioxidants and macular pigment
may be particularly important in subjects highly exposed
to light. These data will need to be confirmed in future
studies.
Besides, cataract surgery was associated with a major
increase in AMD incidence in a few studies
(7,75-81)
,
although not all
(82-83)
. For instance, in a pooled analy-
sis of two major population-based studies (Beaver Dam
and Blue Mountains), eyes which had undergone lens
extraction had a 5.7-fold increased risk of developing
late AMD
(79)
. The reasons for increased risk of AMD
in aphakic and pseudophakic eyes are unknown, but
may include increased light exposure. Indeed, the lens
naturally absorbs ultraviolet light, and, with the lens
yellowing observed with ageing and cataract, also part
of blue light. In this context, use of blue light filters in
the implanted artificial lenses have been proposed
(84)
,
and are currently widely used, although their potential
effect on the reduction of incidence of AMD has not
been evaluated.
Because cataract surgery is the most frequent surgi-
cal procedure in most industrialized countries, the
potential increased risk of AMD in operated eye needs
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