Ginkgo Extract Reduces Visual Field Damage in Patients with Glaucoma

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Reviewed: Quaranta L, Bettelli S, Uva MG, Semeraro F, Turano R, Gandolfo E. Effect of Ginkgo biloba extract on preexisting visual field damage in normal tension glaucoma. Ophthalmology 2003;110:359-364.

Normal tension glaucoma (NTG) is a form of glaucoma in which the intraocular pressure (pressure inside the eye) is normal, but there is optic nerve damage and visual field damage (vision loss). What causes the optic nerve damage is not known, but it may be caused by reduced blood flow to that nerve. Studies have shown that Ginkgo biloba extract (GBE) has a favorable effect on blood circulation. The goal of this study was to evaluate the effect of GBE on preexisting visual field damage of patients with NTG.

Patients (N = 27, 11 men, 16 women, mean age 70.4 years) with visual field damage from NTG participated in this prospective, randomized, placebo-controlled, double-blind, crossover study. Patients in the GBE group randomly received 40 me GBE (24% flavone glycosides, 6% terpencs; FidiaOftal Spa, Catania, Italy) orally, 3 times per day for 4 weeks. This was followed by an 8-week washout period, and then patients received 4 weeks of placebo. Some patients started GBE first, while others started placebo first. Visual fields, intraocular pressure, and heart rate were examined. Complete ocular and systemic examinations were also performed.

No patient reported a difference in taste between the capsules. The group that received GBE prior to placebo had a significant decrease in visual field damage (P < 0.0001). When GBE was discontinued, the improvement was not maintained. This suggests that GBE would need to be taken long-term for the benefits to be maintained. The group that started with placebo had no improvement when measured after the initial period; however, upon taking GBE their visual field significantly improved (P < 0.0001). There were no significant modifications in intraocular pressure, blood pressure, and heart rate. There were no ocular or systemic side effects.

The results suggest that GBE can improve preexisting visual field damage in some individuals with NTG. The precise explanation for the effect is not known. It has been demonstrated that GBE can increase blood flow in the ophthalmic artery in healthy subjects. The patients in this study may have benefited from this effect. It is known that reduced blood flow to the optic nerve plays an important role in the genesis of visual field damage in NTG. Another possibility is that GBE increases cerebral blood flow, which increases blood flow to the eye.

This pilot study offers preliminary results that may be potentially beneficial for the field of ophthalmology. A long-term, randomized, prospective, placebo-controlled trial would help determine if ophthalmology, particularly NTG, would become another of the areas where standardized ginkgo extract shows safe and effective applications.

PHOTO (COLOR): Ginkgo Ginkgo biloba

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By Heather S. Oliff, Ph.D.

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