Could Ginkgo Biloba Help Protect Vision in Glaucoma? Early Study Suggests Improved Blood Flow to the Eye

Summary

For decades, glaucoma treatment has focused primarily on lowering eye pressure. But scientists increasingly recognize that poor blood flow to the optic nerve may also contribute to vision loss.

A small clinical trial found that Ginkgo biloba extract significantly increased blood flow velocity in a major artery supplying the eye. While the study involved healthy volunteers rather than glaucoma patients, the findings helped spark interest in Ginkgo biloba as a potential neuroprotective therapy for glaucoma and other eye diseases.

Key Takeaways

• Researchers investigated whether Ginkgo biloba extract could improve blood flow to the eye.
• The study was a randomized, double-masked, placebo-controlled crossover trial.
• Eleven healthy volunteers received Ginkgo biloba extract and placebo at different times.
• Ginkgo biloba significantly increased blood flow velocity in the ophthalmic artery.
• Eye pressure, blood pressure, and heart rate remained unchanged.
• No significant side effects were reported.
• The study did not evaluate vision improvement or glaucoma progression.
• Larger clinical trials in glaucoma patients are needed to determine whether improved blood flow translates into better visual outcomes.

Why This Study Is Important

Glaucoma is one of the leading causes of irreversible blindness worldwide. Although elevated intraocular pressure (IOP) is the most important known risk factor, many patients continue to lose vision despite successful pressure control.

Over the past several decades, researchers have identified another possible contributor: inadequate blood flow to the optic nerve and retina.

Studies have shown that patients with open-angle glaucoma and normal-tension glaucoma often exhibit abnormalities in ocular circulation, including reduced retinal blood flow and impaired blood vessel regulation. These vascular problems may contribute to optic nerve damage independent of eye pressure.

Because of these findings, scientists have searched for therapies that could improve blood supply to the eye while also protecting vulnerable nerve cells.

One candidate is Ginkgo biloba extract, a botanical supplement widely used in Europe and Asia for circulatory and cognitive health. The extract contains flavonoids and terpene lactones, compounds believed to possess antioxidant, anti-inflammatory, and vascular effects.

Study Design

Type of Study

Researchers conducted a:

• Phase I clinical trial
• Randomized study
• Prospective trial
• Double-masked study
• Placebo-controlled crossover study

This design allowed every participant to receive both active treatment and placebo at different times, reducing individual variability.

Participants

The study enrolled:

• 11 healthy volunteers
• 8 women and 3 men
• Average age: 34 years

Importantly, none of the participants had glaucoma or other eye diseases.

Materials and Methodology

Participants received either:

Ginkgo Biloba Extract (GBE)

• 40 mg capsules
• Taken orally three times daily
• For two consecutive days

Placebo

• Matching placebo capsules
• Taken on a separate study period

A two-week washout period separated the treatment phases. Neither participants nor investigators knew which treatment was being administered during each phase.

Researchers measured:

• Intraocular pressure (IOP)
• Blood pressure
• Heart rate
• Blood flow in ocular arteries

Understanding the Measurements

What Is Color Doppler Imaging?

The primary tool used in the study was Color Doppler Imaging (CDI).

CDI is an ultrasound-based technology that measures blood flow velocity inside blood vessels.

In ophthalmology, CDI can evaluate circulation in arteries supplying the eye and optic nerve.

Which Blood Vessels Were Examined?

Researchers measured blood flow in:

Ophthalmic Artery (OA)

The major artery supplying blood to the eye and orbit.

Central Retinal Artery (CRA)

Provides blood to the retina.

Short Posterior Ciliary Arteries (SPCA)

Supply blood to the optic nerve head and choroid.

What Is End Diastolic Velocity (EDV)?

The primary outcome was End Diastolic Velocity (EDV).

EDV measures blood flow speed during the relaxation phase of the heartbeat.

Higher EDV generally suggests improved blood perfusion and lower downstream vascular resistance.

Results

Significant Increase in Ophthalmic Artery Blood Flow

The most important finding was a statistically significant increase in blood flow velocity within the ophthalmic artery.

End Diastolic Velocity (EDV)

• Before Ginkgo biloba: 6.5 cm/sec
• After Ginkgo biloba: 7.7 cm/sec
• Increase: approximately 23%
• Statistical significance: p = 0.023

Placebo treatment produced no meaningful change.

Trend Toward Increased Peak Blood Flow

Researchers also observed a trend toward higher peak systolic velocity (PSV):

• Before treatment: 29.6 cm/sec
• After treatment: 33.4 cm/sec

Although the increase did not reach statistical significance, it suggested improved blood flow dynamics.

No Changes in Eye Pressure

Importantly, Ginkgo biloba did not affect:

• Intraocular pressure
• Blood pressure
• Heart rate

This suggests the observed blood flow improvement was not simply due to systemic cardiovascular changes.

No Significant Side Effects

Researchers reported:

• No serious adverse events
• No treatment-related discomfort
• Excellent short-term tolerability

Why These Findings Matter

One of the most intriguing aspects of glaucoma research is the growing recognition that glaucoma may be more than a pressure disease.

Many glaucoma patients demonstrate abnormalities in blood flow regulation and vascular function. Improving circulation to the optic nerve could potentially help preserve retinal ganglion cells, the neurons responsible for transmitting visual information from the eye to the brain.

Researchers also noted that Ginkgo biloba possesses antioxidant properties and may provide neuroprotective benefits by reducing free-radical damage and inhibiting platelet-activating factor, a molecule associated with neuronal injury.

These combined vascular and neuroprotective effects make Ginkgo biloba an intriguing candidate for future glaucoma therapies.

What Are the Limitations?

Several important limitations should be considered.

Healthy Volunteers Only

The study did not include glaucoma patients.

Researchers cannot assume the same results would occur in diseased eyes.

Small Sample Size

Only 11 participants were enrolled.

Larger studies are needed to confirm the findings.

Very Short Treatment Period

Participants received Ginkgo biloba for only two days.

Long-term effects remain unknown.

No Vision Outcomes

Researchers measured blood flow but did not evaluate:

• Visual field improvement
• Optic nerve preservation
• Slowing of glaucoma progression

Therefore, the study does not prove that Ginkgo biloba improves vision or prevents blindness.

Bottom Line

This early clinical trial found that Ginkgo biloba extract significantly increased blood flow velocity in the ophthalmic artery without affecting eye pressure, blood pressure, or heart rate.

Although the study involved only healthy volunteers and lasted just two days, the findings provided important evidence that Ginkgo biloba may influence ocular circulation. Combined with its antioxidant and neuroprotective properties, the extract remains an area of ongoing interest in glaucoma research.

For now, the study should be viewed as a promising first step rather than proof that Ginkgo biloba is an effective glaucoma treatment. Future clinical trials in glaucoma patients will be needed to determine whether improved ocular blood flow can translate into meaningful vision preservation.

Study Reference

Chung HS, Harris A, Kristinsson JK, Ciulla TA, Kagemann C, Ritch R. Ginkgo biloba extract increases ocular blood flow velocity. J Ocul Pharmacol Ther. 1999 Jun;15(3):233-40. doi: 10.1089/jop.1999.15.2