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Vitamins
& Eye:
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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