The effect of ginkgo biloba on ocular blood flow

A recent study casts doubt on the ability of ginkgo biloba to affect blood flow in the eye. This might be important for people with cataracts and glaucoma, but the findings are at odds with the prevailing point of view.

Here’s some perspective.

First, the details of the latest study.

  • 15 healthy men took ginkgo biloba extract (EGb761) 240 mg or placebo at different times.
  • Neither the volunteers nor the investigators were aware of the treatment.
  • Before and 3 hours after treatment, a series of measurements were taken using laser Doppler and laser interferometry and tonometry techniques.

And the results.

  • There were significant changes before and after EGb761 treatment
  • But the differences compared to the changes following placebo never reached statistical significance.

The bottom line?
Importantly, the response was measured following just a single dose, not following long-term therapy, which would be closer to what a patient would receive.

By comparison, a review of the literature published in 2001 concluded that ginkgo biloba increased blood circulation to the optic nerve. Both of the studies in this review administered more than one dose.

Here are the details.
46 patients

  • Some with severe visual field disturbances, and others with serious retinal vascular degeneration
  • 160 mg/day Ginkgo extract for 4 weeks, followed by 120 mg/day
  • Resulted in mild but “relevant” improvements considering the severity of the ocular damage at the beginning of the study.

11 healthy volunteers

  • Treated with either 40 mg Ginkgo extract 3 times daily or placebo for 2 days
  • Ginkgo significantly increased blood flow to the ophthalmic artery
  • No change seen in the placebo group.

One other study published in 2003 where patients received 40 mg ginkgo biloba extract or placebo 3 times daily for 4 weeks concluded, “Ginkgo biloba extract administration appears to improve preexisting visual field damage in some patients with NTG [normal tension glaucoma].”

6/21/07 13:23 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.