MyVisionTest News Archive
Jan 16, 2012
Ocular factors associated with AMD in Latinos
The Latino Eye Study found that ocular factors such as cataract, 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.
Read more...
Am J Ophthalmol. 2010 May;149(5):735-40
Tags: racial differences, risk factors, cataract, myopia
The Latino Eye Study found that ocular factors such as cataract, 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
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.
Read more...
Am J Ophthalmol. 2010 May;149(5):735-40
