Natural therapies for ocular disorders, part two: cataracts and glaucoma.

Thorne Research, Inc., P.O. Box 25, Dover, ID 83825,USA.
Alternative medicine review: a journal of clinical therapeutic (Impact Factor: 4.86). 05/2001; 6(2):141-66.
Source: PubMed

ABSTRACT Pathophysiological mechanisms of cataract formation include deficient glutathione levels contributing to a faulty antioxidant defense system within the lens of the eye. Nutrients to increase glutathione levels and activity include lipoic acid, vitamins E and C, and selenium. Cataract patients also tend to be deficient in vitamin A and the carotenes, lutein and zeaxanthin. The B vitamin riboflavin appears to play an essential role as a precursor to flavin adenine dinucleotide (FAD), a co-factor for glutathione reductase activity. Other nutrients and botanicals, which may benefit cataract patients or help prevent cataracts, include pantethine, folic acid, melatonin, and bilberry. Diabetic cataracts are caused by an elevation of polyols within the lens of the eye catalyzed by the enzyme aldose reductase. Flavonoids, particularly quercetin and its derivatives, are potent inhibitors of aldose reductase. Glaucoma is characterized by increased intraocular pressure (IOP) in some but not all cases. Some patients with glaucoma have normal IOP but poor circulation, resulting in damage to the optic nerve. Faulty glycosaminoglycan (GAG) synthesis or breakdown in the trabecular meshwork associated with aqueous outflow has also been implicated. Similar to patients with cataracts, those with glaucoma typically have compromised antioxidant defense systems as well. Nutrients that can impact GAGs such as vitamin C and glucosamine sulfate may hold promise for glaucoma treatment. Vitamin C in high doses has been found to lower IOP via its osmotic effect. Other nutrients holding some potential benefit for glaucoma include lipoic acid, vitamin B12, magnesium, and melatonin. Botanicals may offer some therapeutic potential. Ginkgo biloba increases circulation to the optic nerve; forskolin (an extract from Coleus forskohlii) has been used successfully as a topical agent to lower IOP; and intramuscular injections of Salvia miltiorrhiza have shown benefit in improving visual acuity and peripheral vision in people with glaucoma.

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    ABSTRACT: Oxidative mechanisms are believed to play an important role in the pathogenesis of cataract, the most important cause of visual impairment at advanced age. To determine the body's antioxidant status as well as its lipid peroxidation levels, both blood and lens parameters were evaluated. This study was performed on the blood samples and lenses obtained from 46 patients diagnosed as having cataract and 20 control subjects. The control group was composed of 10 women and 10 men who do not smoke. Control subjects without any lens opacity or vacuoles when observed with a slit lamp were recruited on the same exclusion criteria as far as disease and treatment were concerned. No antioxidant medicines were used. They were all healthy individuals without any systemic diseases. Superoxide dismutase (SOD), glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GSSG-Red) activities in red blood cell (RBC) lysates as well as whole blood glutathione (GSH) and plasma thiobarbituric acid reactive substances (TBARS), the indicator of lipid peroxidation concentrations, were determined quantitatively both in the blood samples and the lenses of the patients with senile and diabetic cataracts. Whole blood GSH values, and erythrocyte SOD activities were significantly lower in the cataractous patients than those in the control group. The values in the diabetic cataractous group were also less than those in the senile cataractous group. Significantly decreased erythrocyte GSSG-Red and G6PD activities were detected in the diabetic cataractous group. Plasma TBARS values were higher both in the senile and diabetic groups when compared to those in the control group. Significantly decreased values were observed for GSSG-Red activities and TBARS values in the lenses of the senile cataractous patients in comparison with those in the diabetic cataractous patients. The lens GSH values were found to be higher in the senile cataractous group than the values obtained in the diabetic cataractous group. A strong correlation was found between lens GSH and lens TBARS concentrations in the diabetic group. This emphasized the vital role of GSH as an antioxidant in the lens over the other antioxidant parameters, e.g., enzymes, and the oxidative stress is at the highest level in lens.
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