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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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