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Introduction:

The botanical Ginkgo biloba has been extensively examined for its cognitive effects in patients with dementia. Recently, a six-month double blind trial conducted at UCLA found significant improvement in verbal recall among subjects with age-associated memory impairment (1). Using positron-emission tomography, the researchers reported that improved recall correlated with better function in key brain memory centers of those taking ginkgo supplements. The effects of ginkgo are attributed to its ability to enhance cerebral blood flow and provide antioxidant activity.

Over the past decade, research has identified non-pressure dependent risk factors for glaucoma, including cerebral and ocular ischemia. There is increasing awareness that the prevalence of normal-tension glaucoma (NTG) is greater than previously realized, and that progressive damage can occur even with IOP-lowering intervention. Since Ginkgo has been shown to increase ocular blood flow (2), the effects of a ginkgo extract on pre-existing visual field damage in normal tension glaucoma was evaluated in a prospective, randomized, double-blind crossover trial (3).

Trial Results:

Twenty seven patients with bilateral visual field damage resulting from NTG received 120 mg of ginkgo extract (40 mg, 3x daily) for 4 weeks, followed by a wash-out period of 8 weeks, then 4 weeks of placebo treatment. Other patients underwent the same regimen, but took the placebo first and ginkgo last. Visual field tests, performed at baseline and at the end of each phase of the study, were evaluated for changes in visual field and any ocular or systemic complications.

After ginkgo treatment, a significant improvement in visual field indices was observed.

No significant changes were found in intraocular pressure, blood pressure, or heart rate after placebo or ginkgo treatment. The investigators concluded that Ginkgo biloba is a useful therapy for some patients with NTG. An accompanying editorial in Ophthalmology points out that the mechanisms of ginkgo are plausible, and that the beneficial effects were not maintained in this study after discontinuation of ginkgo treatment. Both of these observations lend credence to the findings.

References

1. Ercoli L et al. Society for Neuroscience Meeting, New Orleans, November, 2003
2. Chung HS et al. Ginkgo biloba extract increases ocular blood flow velocity. J Ocul Pharmacol Ther 15:233-40, 1999.
3. Quaranta L et al. Effect of Ginkgo biloba extract on preexisting visual field damage in normal tension glaucoma. Opthalmol 110:359-62 (discussion 362-4), 2003.