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In
the United States, an estimated 80 millions Americans have
potentially blinding eye diseases, & 1.1 million people
are legally blind. Approximately 12 million people have some
degree of visual impairment that cannot be corrected by glasses,
& more than 100 millions people need corrective lenses
to see properly. By 1995, the economic impact of visual disorders
& disabilities was approximately $38.4 billion each year.
(Source: Courtesy of National Eye Institute, Optics Laboratory,
and Inc 1998-2000)
Free
radicals & Diminished Vision
As
people age, they are often faced with diminished vision stemming
from age related maculae degeneration. (ARMD) or cataract.
ARMD the leading cause of blindness in people over the age
of 55 affects an estimated one million Canadians. The prevalence
of ARMD is expected to increase as the population ages. According
to a recent poll, aging North Americans fear blindness more
than any other disability.
Many scientists hypothesize that free radicals (Molecules
with an unbalanced pair of electrons) generated by ultra-violet
rays of sun and blue light play a role in the development
of both ARMD and cataracts. Free radicals seem to cause oxidation
and loss of pigments in the macula over time, and also oxidize
lens proteins, which clump together and precipitate, causing
parts of the lens to become opaque.
Anti-oxidants
compounds such as Vitamin A, C and E, and trace elements such
as Selenium, Zinc, Manganese and Copper appear to help cells
fight off free radical damage. As people age, their bodies
loss these natural defense mechanisms. While the results of
major clinical trials will not be reported for several years,
many vision care specialists are advising their patients to
supplement their diets with antioxidants rich vitamins
(A, D, E) and minerals (Zinc, Copper, manganese &
Selenium) as a precaution.
Association
between Nutrition & Cataract
Blindness
due to opacities of the lens, or cataract afflicts over 50
million persons worldwide. In the USA over 541,000 cataracts
extraction are done annually at a cost of over $3.8 billion.
Conservative estimates indicate that the prevalence of cataracts
in Americans aged 65-75 & 75-85 estimated that the need
for cataract extraction would be diminished by half if onset
of cataract could be delayed by only ten years. Hypothesis
regarding the etiology of cataract include oxidative perturbations
of proteins metabolism, diverse pathologic conditions, &
perhaps glycation of lens proteins. Biochemical evidence suggest
that compounds like, carotenoids (vitamin A), ascorbate (vitamin
C) etc can delay photooxidative damage to lens proteins. Role
in lens metabolism for selenium have been suggested. Elucidation
of mechanism by which caloric restriction delays cataract
development is a promising area of current research.
(Taylor A. Nutr Rev 1989;47:225-234)
Antioxidants
in Cataract Prevention
The
ocular lens, which is continually exposed to the light and
ambient oxygen, is at high risk of the photo oxidative damage
resulting in the cataracts. Oxygen free radicals appear to
improve not only lens crystalline, which will aggregate, &
precipitate forming opacities but also proteolytic enzymes
whose function it would be to eliminate the damaged proteins.
The lens contains vitamins C, E and presumably beta-carotene
as another line of defense. The studies in different animal
species have demonstrated a significant protective effect
of vitamins C &E against light-induced cataracts. Sugar
and steroid cataracts were prevented as well.
Epidemiological evidence in humans suggest that persons with
comparatively higher intakes are at a reduce risk of cataract
development.
These
positive findings establish by several research groups justify
extensive intervention trials with antioxidant vitamins in
humans using pre-senile cataract development.
(Gerster H. Z Ernahrungswiss 1989;28:56-75)
Scientific
basis for Medical therapy of Cataracts by Antioxidants
Cataract
is one of the major cause of age-dependent visual impairments
of blindness. The geographical distribution of cataract is
known to be associated with the intensity and duration of
sunlight-especially of the ultra-violet frequency at particular
places. Exposure of humans and animals to oxygen has also
been known to result in cataract formation. Studies described
in this communication indicate that the ocular lens is physiologically
damaged when exposed to an environment of active species of
oxygen, commonly referred to as oxyradicals. Several photo
chemical and nonphotochemical models have been described.
The result suggests that intra ocular generation of active
oxygen may constitute as significant risk factor in the over
all pathogenesis of senile cataracts. The catratogenic effects
of oxyradicals, however, can be disillusioned by nutritional
and metabolic antioxidants such as ascorbate and Vitamin E.
These agents, therefore, may be useful for the prophylaxis
or therapy against cataracts.
(Varma SD. Am J Clin Nutr 1991;53:335S-345S)
Bottom
Line
It may be next to impossible these days to obtain adequate
amount of minerals from diet alone. Since delicate nutrients
have been destroyed by food processing. The entire Canadian
population may there fore benefit from taking supplements
containing “Ocular Vitamins for the prevention of age
related macular degeneration”.
(Barbara G. Ogle, consultant Pharmacist and Community practitioner
in Vancouver BC)
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