Ocular factors associated with AMD in Latinos
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cataract surgery, and refractive errors associated with early
age-related macular degeneration (AMD) lesions found in Latinos are
consistent with those in non-Hispanic Whites.
Previous population-based studies among Caucasians have identified
possible associations of various ocular factors with AMD. These
include hyperopia with both early and advanced AMD, cataracts with
early AMD, and iris color with both early and advanced AMD. Pooled
data from the Blue Mountains and Beaver Dam Eye studies found an
association between cataract surgery and advanced AMD as too did
pooled data from the Salisbury Eye evaluation Survey, Proyecto VER and
the Baltimore Eye Survey
Methods &anp; Results
The Los Angeles Latino Eye Study (LALES) is a population-based,
cross-sectional study of adult Latinos aged 40 years and older, living
in six census tracts in the city of La Puente, California. This city
was chosen because of its large, stable Latino population and its
similar socioeconomic demographic profile to that of Latinos in the
U.S.
Ophthalmic examination included subjective refraction, measurement of
axial length, evaluation of iris color, Lens Opacities Classification
System II (LOCS II) grading of cataracts, and stereoscopic macular
photographs for AMD lesions. Generalized estimating equation analysis
incorporated data from both eyes to estimate odds ratios (OR) adjusted
for covariates.
After controlling for confounders (age, gender, and smoking), prior
cataract surgery was associated with advanced AMD (OR, 2.8; 95% CI,
1.01, 7.8), increased retinal pigment (OR, 1.6; 95% CI, 1.02, 1.5),
and retinal pigment epithelial depigmentation (OR, 2.2; 95% CI, 1.1,
4.4). The presence of any lens opacity was associated with soft drusen
(OR, 1.2; 95% CI, 1.002, 1.5). Longer axial length (per mm) was
associated with decreased odds of soft drusen, increased retinal
pigment, and geographic atrophy (GA) (ORs, 0.8 [95% CI, 0.7, 0.9], 0.8
[95% CI, 0.7, 0.9], 0.7 [95% CI, 0.5, 0.9], respectively). Myopia was
inversely associated with soft drusen (OR, 0.8; 95% CI, 0.7, 0.99).
Lighter-colored irises were associated with GA (OR, 5.0; 95% CI, 1.0,
25.3).
Discussion & Conclusions
This report presents the association of ocular factors and AMD lesions
using data from the Los Angeles Latino Eye Study. Associations between
prior cataract extraction and early and advanced AMD, nuclear
sclerotic cataract and soft drusen, light iris color and geographic
atrophy were found. Longer axial length was negatively associated with
early AMD lesions and geographic atrophy.
The relationship between cataract, cataract surgery and AMD has been
investigated in many previous epidemiologic studies with inconsistent
findings. Cataract and AMD may share one or more risk factors, or each
may serve as a biomarker of ageing. We found a significant association
of nuclear sclerotic cataract and soft drusen but not advanced AMD.
Cataract surgery prior to entry into the LALES was associated with
three times increased risk of advanced AMD, doubled the risk of
decreased retinal pigment and increased the risk of increased retinal
pigment. These findings are consistent with pooled findings from other
prevalent studies that included the Salisbury Eye evaluation Survey,
Proyecto VER and the Baltimore Eye Survey.
Findings from many prospective studies have reported similar
associations. Cataract surgery was associated with long term incidence
of advanced AMD in the Beaver Dam Eye Study (BDES) and in pooled
findings from the BDES and BMES. It is not known what the AMD status
of these eyes were prior to cataract surgery, and whether they had
earlier surgery due to increased symptoms from early AMD as well as
cataract, or whether inflammation related to the surgery was the cause
of the incident advanced AMD and early AMD lesions. Recently, the
Rotterdam Eye study reported an association of cataract surgery with
incident geographic atrophy (OR, 3.44; 95% CI, 1.68–7.08) after
adjustment for co-variates. There was no significant association of
cataract surgery with exudative AMD in that cohort20. However, more
recently, The Age Related Eye Disease Study (AREDS), a prospective
study of 4757 participants aged 55 to 80 years enrolled from 1992 to
1998 from retinal clinics in the US did not find an association
between cataract surgery and progression to advanced AMD.
Although our positive findings of an association of AMD with cataract
and cataract surgery are in agreement with a number of cross-sectional
and longitudinal studies among non Hispanic Whites, the relationship
between cataract and AMD is still not clear.
In LALES, myopia was associated with decreased odds of soft drusen and
longer axial length was associated with decreased odds of geographic
atrophy. There was no association of hyperopia with AMD. This lack of
an association with hyperopia is consistent with findings from the
BDES but inconsistent with several case-controlled and cross-sectional
studies which have found an association between AMD and hyperopia.
Further, epidemiological studies, including the BMES and Rotterdam Eye
Study found an association between hyperopia and early AMD.
In the Rotterdam Eye Study, each diopter of hyperopia increased the
risk of early AMD prevalence (OR: 1.09 (95% CI: 1.04–1.14)) and
advanced AMD (OR: 1.09; 95% CI: 1.00–1.19) and in the Blue Mountains
Eye Study, each diopter towards hyperopia also increased the risk of
early AMD (OR: 1.1; 95% CI: 1.0–1.2) and moderate to high hyperopia
doubled the risk of early AMD (OR, 2.0; CI, 1.2–3.4). Results from
the Beijing eye study also found hyperopia to be statistically
significantly associated with early AMD. One of the postulated
mechanisms for how hyperopia results in AMD is that eyes with
hyperopia are thought to have increased scleral rigidity due to a
shorter axial length resulting in an increased choroidal vascular
resistance and impaired retinal pigment epithelial function. This
supports a paper by Friedenwald who reported that the coefficient of
scleral rigidity was inversely proportional to axial length, directly
proportional to age and could be considered as an "index of
senescence". In LALES, although, we found no association with
hyperopia, our finding of a protective effect of both myopia and
longer axial length for soft drusen is consistent with this.
Age-related macular degeneration appears to be less prevalent in
pigmented races. A number of studies have reported an association of
advanced AMD in eyes with blue or lighter colors compared with dark
brown irides. We found a fivefold increased risk of geographic atrophy
in persons with lighter colored irides. Although the risk of any
advanced AMD in persons with light colored irides was doubled, this
was only of borderline significance. It has been postulated that the
lower risk of age related macular degeneration among participants with
darker irides may be that those persons also have more melanin in
their choroid and retina and melanin may act as a free radical
scavenger and thus provide protection from light-induced oxidative
damage to the retina. An alternative explanation for this finding may
be an underlying genetic factor correlated with light iris color.
However, other studies have not found any significant association of
iris color with AMD. The reasons for this disparity are not evident.
In summary, we found a number of cross-sectional associations
including one between prior cataract extraction and advanced AMD,
consistent with findings in non Hispanic whites. The relationship of
these risk factors to incident early and advanced AMD in Latinos are
required to further establish these relationships among persons of
different ethnicities.
Am J Ophthalmol. 2010 May;149(5):735-40
http://www.ncbi.nlm.nih.gov/pubmed/20138605
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