Too Much Sunlight, Too Few Antioxidants Places Older
Adults at Risk for Eye Disease
Second study finds older diabetes patients more
likely to have eye disease than those without the disease
Oct.
13, 2008 - A European study suggests that the combination of low plasma
levels of antioxidants and blue light exposure from the sun is
associated with certain forms of the eye disease age-related macular
degeneration (AMD), the most common cause of blindness in senior
citizens, according to a report in the October issue of Archives of
Ophthalmology, one of the JAMA/Archives journals.
"The retina is vulnerable to the damaging effects
of light," the authors write as background information in the article.
"While wavelengths in the UV radiation range are largely absorbed by the
cornea and lens, the retina is exposed to visible light, including blue
light."
Animal and laboratory studies suggest blue light
may damage the retina and contribute to the development of AMD, which
occurs when the area of the retina (macula) responsible for sharp vision
deteriorates.
Antioxidant enzymes - including vitamins C and E,
the carotenoids (lutein and zeaxanthin) and zinc - may protect against the
harmful effects of blue light on the retina.
Astrid E. Fletcher, Ph.D., of the London School of
Hygiene & Tropical Medicine, and colleagues measured levels of these
nutrients in the blood of 4,753 older adults (average age 73.2) who were
part of the European Eye Study.
Age-related macular degeneration is the most common
cause of legal blindness in senior citizens - people age 65 or older - and is expected to
become an increasingly common and costly health issue as the number of
older people in US increases.
Diabetic retinopathy is the
most common cause of legal blindness in working-age Americans.
Currently, there are an estimated 21 million people with diabetes.
Participants also were interviewed about their
lifetime sunlight exposure and had photographs taken of their retinas to
detect AMD.
Of the 4,400 participants with complete information
available, 2,117 did not have AMD, 101 had neovascular (advanced,
involving the formation of new blood vessels) AMD and 2,182 had
early-stage AMD.
Overall, there was no association between blue
light exposure and neovascular or early AMD. However, blue light
exposure was associated with neovascular AMD in the one-fourth of
individuals with lowest antioxidant levels.
"In particular, the combination of blue light
exposure in the presence of low levels of zeaxanthin, alpha-tocopherol
[vitamin E] and vitamin C was associated with a nearly four-fold odds
ratio of neovascular AMD," the authors write.
Key recommendations from the results include
ensuring the intake of key antioxidants, which can be accomplished by
consuming recommended dietary intake levels of vitamin C and zinc and
increasing consumption of carotenoid-rich fruits and vegetables, the
authors note.
In addition, individuals should take steps to
reduce the exposure of the retina to blue light, such as wearing
broad-brimmed hats and sunglasses when outdoors.
"In the absence of cost-effective screening methods
to identify people in the population with early AMD, we suggest that
recommendations on ocular protection and diet target the general
population, especially middle-aged people," they conclude.
Vision Loss More Common in Older People with
Diabetes
A second study in the same issue of
Archives of
Ophthalmology reports that visual impairment in older people appears to
be more common in people with diabetes than in those without the
disease.
Approximately 14.6 million Americans had diagnosed
diabetes mellitus in 2005 and another 6.2 million had undiagnosed
diabetes, according to background information in the article.
It is estimated that the number of individuals with
diagnosed diabetes will increase to 48.3 million by 2050.
"Diabetic retinopathy [damage to the retina caused
by diabetes], one of the most common microvascular complications of
diabetes, is considered to be one of the major causes of blindness and
low vision," the authors write.
Although studies suggest that controlling glucose
and blood pressure have reduced the rate of retinal diseases, other
ocular conditions suffered by diabetic patients, such as cataract and
glaucoma, may increase the risk of visual impairment. Additionally,
decreased vision caused by an abnormal shape of the cornea is also
common among people with diabetes.
Xinzhi Zhang, M.D., Ph.D., and colleagues at the
Centers for Disease Control and Prevention, Atlanta, used data from the
National Health and Nutrition Examination Surveys from 1999 to 2004,
which included 1,237 adults with diabetes (average age 59) and 11,767
adults without the disease (average age 45) and also measured their
visual acuity before and after optical correction.
Participants vision was tested while they were
wearing any glasses or contacts they typically used, and their
demographic information was also noted.
An estimated 11 percent of American adults with
diabetes had some form of visual impairment (3.8 percent uncorrectable
and 7.2 percent correctable), while only 5.9 percent of those without
diabetes had some form of visual impairment (1.4 percent uncorrectable
and 4.5 percent correctable).
"People with diabetes were more likely to have
uncorrectable vision impairment than those without diabetes, even after
controlling for selected other factors," the authors write.
"Our findings also suggest a strong association
between visual impairment (correctable and uncorrectable) and older age,
member of racial/ethnic minorities, lower income and lack of health
insurance, all independent of diabetes status."
"The high prevalence of visual impairment among
people with diabetes indicates a need for diverse public health
strategies to reduce the burden of both correctable and uncorrectable
visual impairment," the authors conclude.
"It is important to identify and pursue ways to
increase access to eye care for everyone and to correct visual
impairment, where possible, to diminish morbidity and mortality due to
impaired vision."
Keep up with the latest news for senior citizens, baby
boomers
Oct.
13, 2008 - A European study suggests that the combination of low plasma
levels of antioxidants and blue light exposure from the sun is
associated with certain forms of the eye disease age-related macular
degeneration (AMD), the most common cause of blindness in senior
citizens, according to a report in the October issue of Archives of
Ophthalmology, one of the JAMA/Archives journals. 
A second study in the same issue of
Archives of
Ophthalmology reports that visual impairment in older people appears to
be more common in people with diabetes than in those without the
disease.