Kay wrote:Does Vitamin C thin the blood and is it helpful in glaucoma patients?
Nutrition and Glaucoma
For decades, eye doctors have approached glaucoma as a loss of peripheral vision resulting from optic nerve damage caused by elevated fluid pressure in the eye. However, eyes with normal fluid pressure can also lose peripheral vision. Now researchers suspect a nerve toxin may be involved in the common form of glaucoma. Glaucoma patients exhibit an abnormally high concentration of glutamate in the vicinity of the optic nerve.17 Glutamate is a primary chemical used in the transmission of optic nerve impulses. Housed inside the nerve sheath, it is innocuous. As optic nerves die off at a normal rate and release small amounts of glutamate, surrounding Muller cells detoxify the area. But glutamate may overwhelm the Muller cells and destroy surrounding cells, thus releasing more nerve-toxic glutamate, resulting in an accelerated loss of vision that is typically observed in the end stages of glaucoma.
While nerve-protective drugs may take years to develop, an array of natural nerve protectors may be able to minimize glutamate toxicity. These include vitamin B12 (methylcobalamin),<18 SAMe (S-adenosylmethionine),18 ginkgo (Ginkgo biloba),19 vitamin E,19 coenzyme Q10,19 folic acid,20 and magnesium.21
Japanese researchers prescribed 28 glaucoma patients a high oral-dose of 1,500 mcg/day vitamin B12 for five years in an open-label study to evaluate the vitamin's influence on vision. The patients receiving B12 experienced less measurable loss of peripheral vision, more stable visual acuity, and better control of eye fluid pressure compared to a group that did not take B12.22 The effects of vitamin B12 are attributed to the preservation of myelin, which insulates nerve cells. Results of this study were achieved with methylcobalamin, a readily absorbable form of vitamin B12.
Cyanocobalamin, the more common form of vitamin B12 present in vitamin supplements, has not been effective in other studies of optic nerve disorders.23
Various studies reveal that Greenland Eskimos have lower rates of glaucoma than other Caucasian populations, an observation attributed to the consumption of omega-3 fish oil. Omega-3 fats appear to help prevent optic nerve disorders. A proprietary combination of DHA-rich fish oil, vitamin E, and vitamin B complex widened the visual field of 30 glaucoma patients within 90 days in an open-label, nonrandomized study.24
In animal studies, researchers were able to lower ocular fluid pressure, a measure of glaucoma, by injecting a very large dose of 0.2 mL/day cod liver oil. Reduction was from 21 mmHg to 18, with injections of 1 mL/day lowering pressure to 14.5 mmHg.25
There is also evidence that lutein and zeaxanthin also help protect the optic nerve. The nerve layer of the retina, near where nerve cells exit the eye and connect to the brain, is protected from oxidative damage by lutein. Researchers have found that a lack of lutein in this nerve bundle may be an early sign of glaucoma.26
Other Eye Disorders
The aqueous fluid in the eye delivers antioxidants to the front of the inner eye, which helps to keep the fluid drain unobstructed. This fluid drains out of the eye in a controlled manner that maintains the shape and fluid pressure inside the eye. When drainage is blocked, fluid pressure rises and can impinge upon peripheral optic nerve cells at the back of the eye, narrowing side vision.
Glucosamine sulfate and vitamin C may counter fluid drain swelling. In a preliminary, uncontrolled 1998 U.S. pilot study of two patients, an unreported daily amount of glucosamine sulfate substantially reduced abnormally high fluid pressure over the short term.27 Vitamin C may help by maintaining the collagen structure of the fluid drain. 28,29 Taking 500 mg vitamin C four times a day moderately and significantly reduces eye fluid pressure in humans.30,31 Typical recommended dosages of glucosamine for collagen support are 1,500 mg/day.
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