Preliminary evidence points to the influence of free-radical formation and the development and progression of many forms of retinopathy.56 Antioxidant formulas have long been the frontline defense in preventing and managing retinopathy. With properties that include free-radical scavenging, preventing protein glycosylation, and decreasing capillary permeability and fragility, it is no wonder that vitamin C is chief among these therapies.57-60 Vitamin E, also a potent intracellular antioxidant, is considered to be effective, at a level of 1,200 international units (IU) per day or more, for preventing and treating similar conditions.61 Vitamins C and E have been shown, in limited investigations, to be present in lower levels in patients with diabetes compared to healthy controls.62,63 In addition, vitamin E has been shown to protect people with very high cholesterol levels from developing retinopathy.64 A combination of 500 mcg of selenium, 800 IU of vitamin E, 10,000 IU of vitamin A, and 1,000 mg of vitamin C, taken each day for several years, has reduced diabetic retinopathy in a single research study.65 Additional research has yielded similar benefits from the administration of alpha-lipoic acid, a powerful inhibitor of oxidative glycosylated proteins.66
Researchers have found an increase in activity of the enzymatic diacylglycerol protein kinase C (DAG-PKC) pathway in the retinas of animals with diabetes.67 This increased enzyme activity appears to interfere with normal circulation to the retina. Vitamin E has been found to normalize the activity of the DAG-PKC pathway, which leads to improved retinal blood flow. Research has shown an additional possible mechanism for improved retinal blood flow via supplementation with vitamin E because of its influence on decreasing platelet aggregation.68 Low blood levels of magnesium, a nutrient that is vital to vascular health and integrity, have been linked to DR.69,70 In a study of 71 people with insulin-dependent diabetes, subjects were divided into two groups, depending on the severity of their DR. All subjects had some degree of magnesium deficiency. The subjects with the most severe DR had the most significant deficiency of the mineral.70 However, using magnesium supplementation to treat DR has not been fully studied. In a preliminary analysis, a group of researchers proposed that vitamin B6 supplementation could be used to prevent diabetic retinopathy.71 The researchers studied data gathered over a period ranging from 8 months to 28 years. The data indicated that patients who tookavitamin B6 supplement seemed to have an absence of retinal involvement. Bioflavonoids, such as quercetin, hesperidin, and naringin, are known to be involved in sorbitol metabolism and the additional development of oxygen free radicals. Thus, when treating patients with diabetes, these bioflavonoids should be considered as a means of inhibiting the enzyme aldose reductase.72 Although human studies have not been done using quercetin to treat retinopathy, many natural-medicine doctors prescribe 400 mg of quercetin three times per day for patients with diabetes.
Botanical medications that have been helpful for treating DR include:
Vaccinium myrtillus (bilberry), standardized to contain 25% anthocyanosides (a fla-vonoid that stabilizes connective tissues73 and decreases capillary fragility74), produces powerful antioxidant effects and appears to have a particular affinity for the retina. Such an extract, when taken in doses between 80 and 160 mg, three times per day, has benefited patients with DR.75
A standardized extract of Ginkgo biloba (ginkgo) has been shown to improve impaired color vision in people with DR.76 The extract was standardized to 24% glycosides. In animal experimentation, ginkgo had significantly greater efficacy for reducing DR after two months compared to animals that were given a placebo. The effect was attributed to this herb's antioxidant effects.77 Most often, 60 mg of an extract is taken two to four times per day.
Improving blood flow, normalizing blood-sugar levels, and correcting for underlying metabolic disturbances appears to be the main therapy for retinal pathology. Considerable evidence points to the benefits of potent antioxidant supplements. Vitamin E is the major choice at this time. However, like many other popular ACM modalities, extensive prospective clinical studies have not been conducted. The future seems bright indeed for patients with DR as more research emphasis is pushed toward ACM studies on treating this condition.
MACULAR DEGENERATION: DESCRIPTION AND ETIOLOGY
Macular degeneration (MD), a group of diseases associated with loss of the central vision portion of ocular activity, is marked by damage to the pigment and neural and vascular layers of the macula. The leading cause of blindness among Caucasian Americans is age-related MD,
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