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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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