In a double-blind study, supplementation with a standardized extract of Ginkgo biloba in the amount of 40 mg three times a day for four weeks partially reversed visual field damage in people with one type of glaucoma (normal tension glaucoma).³

Several studies have shown that supplementing with vitamin C can significantly reduce elevated intraocular pressure in individuals with glaucoma.⁴ These studies used at least 2 grams per day of vitamin C; much larger amounts were sometimes given. Higher quantities of vitamin C appeared to be more effective than smaller amounts.

Doctors often suggest that people with glaucoma take vitamin C to “bowel tolerance.”⁵ The bowel-tolerance level is determined by progressively increasing vitamin C intake until loose stools or abdominal pain occurs, and then reducing the amount slightly, to a level that does not cause these symptoms. The bowel tolerance level varies considerably from person to person, usually ranging from about 5 to 20 or more grams per day. Vitamin C does not cure glaucoma and must be used continually to maintain a reduction in intraocular pressure.

Studies in healthy humans, including at least one double-blind trial, have repeatedly shown that intraocular pressure is lowered by direct application of forskolin, a constituent of the Ayurvedic herb Coleus forskohlii .^{6 , 7} Until ophthalmic preparations of coleus or forskolin are available, people with glaucoma should consult with a skilled healthcare practitioner to obtain a sterile fluid extract for use in the eyes. Direct application of the whole herb to the eyes has not been studied and is not advised.

Alpha lipoic acid (150 mg per day for one month) improves visual function in people with some types of glaucoma.⁸

Dan shen (Salvia miltiorrhiza), a traditional Chinese herb, used either alone or combined with other Chinese herbs for 30 days was reported to improve vision in people with glaucoma.⁹ However, the herb was administered by muscular injection, a preparation that is not readily available in North America or Great Britain. It is not known whether oral use of the herb would have the same effect.

Surveys have shown that Inuit people, who consume large amounts of omega-3 fatty acids, have a much lower incidence of some types of glaucoma than do Caucasians. Although there have been no studies on the use of omega-3 fatty acids to treat glaucoma, one study found that cod liver oil (a rich source of omega-3 fatty acids) reduced intraocular pressure in animals.¹⁰

Magnesium can dilate blood vessels. One study looked at whether magnesium might improve vision in people with glaucoma by enhancing blood flow to the eyes. In that trial, participants were given 245 mg of magnesium per day. Improvement in vision was noted after four weeks, but the change did not reach statistical significance.¹¹

Supplementing with 0.5 mg of melatonin lowered intraocular pressure of healthy people,¹² but there have been no studies on the effects of melatonin in people with glaucoma.

Many years ago, the flavonoid rutin was reported to increase the effectiveness of conventional medication in people with glaucoma.¹³ The amount used—20 mg three times per day—was quite moderate. In that study, 17 of 26 eyes with glaucoma showed clear improvement. Modern research on the effects of rutin or other flavonoids in people with glaucoma is lacking.