Can Ginkgo Biloba Improve Blood Flow to the Eye in Glaucoma? New Research Suggests It May

Summary

For patients with normal-tension glaucoma, vision loss can continue even when eye pressure remains within the normal range. A randomized clinical trial published in the Korean Journal of Ophthalmology found that Ginkgo biloba extract significantly improved blood flow around the optic nerve in patients with normal-tension glaucoma, providing further evidence that vascular health may play an important role in glaucoma management.

While the study did not demonstrate immediate improvements in vision, the findings suggest that enhancing ocular circulation could become an important complementary strategy alongside traditional eye pressure-lowering therapies.

Key Takeaways

• Researchers investigated whether Ginkgo biloba extract (GBE) could improve blood flow around the optic nerve in patients with normal-tension glaucoma (NTG).
• Thirty patients participated in a randomized, double-masked, placebo-controlled clinical trial.
• Patients received 80 mg of Ginkgo biloba extract twice daily for four weeks.
• Ginkgo significantly increased blood flow in multiple regions surrounding the optic nerve compared with placebo.
• Improvements were observed in blood flow, blood volume, and blood velocity in several retinal and optic nerve regions.
• No significant changes were found in intraocular pressure (IOP) or visual field measurements during the short study period.
• No ocular or systemic side effects were reported.
• Researchers concluded that Ginkgo biloba may offer a beneficial vascular effect in patients with normal-tension glaucoma.

Why Is This Study Important?

For decades, glaucoma treatment has focused primarily on reducing intraocular pressure (IOP). While lowering eye pressure remains the only proven way to slow glaucoma progression, many patients with normal-tension glaucoma continue to lose vision despite having normal eye pressure.

This has led scientists to explore another explanation: inadequate blood flow to the optic nerve.

The vascular theory of glaucoma suggests that reduced circulation may deprive the optic nerve of oxygen and nutrients, leading to gradual damage and vision loss. Several studies have linked glaucoma progression to:

• Poor ocular blood flow
• Blood vessel dysfunction
• Migraine and vasospasm disorders
• Cardiovascular disease
• Reduced blood pressure
• Microvascular ischemia

Because Ginkgo biloba has been shown to improve circulation and possesses antioxidant properties, researchers wanted to determine whether it could improve blood flow directly within the eyes of glaucoma patients.

What Is Ginkgo Biloba?

Ginkgo biloba is a plant extract derived from the leaves of one of the world's oldest tree species.

The standardized extract contains several biologically active compounds, including:

• Flavonoid glycosides
• Terpene lactones
• Ginkgolides
• Organic acids

Researchers believe these compounds may:

• Improve blood vessel dilation
• Enhance microcirculation
• Reduce blood viscosity
• Improve oxygen delivery
• Protect cells from oxidative stress
• Support neuronal health

These effects have made Ginkgo biloba a subject of interest in conditions involving circulation and neurodegeneration, including glaucoma.

Study Design

Type of Study

The investigators conducted a:

• Randomized clinical trial
• Double-masked (double-blind) study
• Placebo-controlled study
• Prospective intervention trial

This type of study design helps minimize bias and provides stronger evidence regarding treatment effectiveness.

Who Participated?

The study enrolled:

• 30 patients with normal-tension glaucoma
• Adults between 18 and 80 years of age
• Patients with documented optic nerve damage and visual field loss despite normal eye pressure

Participants were randomly divided into two groups:

Ginkgo Group

• 15 patients
• Received 80 mg Ginkgo biloba extract twice daily
• Total daily dose: 160 mg
• Treatment duration: 4 weeks

Placebo Group

• 15 patients
• Received matching placebo capsules
• Treatment duration: 4 weeks

Neither the participants nor the researchers knew who received Ginkgo or placebo until the study ended.

How Did Researchers Measure Blood Flow?

Heidelberg Retina Flowmeter (HRF)

The primary outcome of the study was ocular blood flow.

Researchers used a sophisticated imaging device called the Heidelberg Retina Flowmeter (HRF), which measures microcirculation within the retina and optic nerve head.

Unlike standard eye examinations, the HRF can quantify blood movement within tiny retinal vessels.

Understanding the Measurements

The HRF evaluated three important blood flow parameters:

Blood Flow

Blood flow measures the amount of blood moving through a specific tissue area over time.

Higher values generally indicate improved circulation.

Blood Volume

Blood volume reflects the amount of blood present within a tissue region.

Increased volume may suggest improved vascular supply.

Blood Velocity

Blood velocity measures how quickly blood is moving through vessels.

Higher velocity can indicate improved delivery of oxygen and nutrients.

Areas Evaluated

Researchers measured circulation in ten separate regions surrounding the optic nerve, including:

• Nasal peripapillary retina
• Temporal peripapillary retina
• Neuroretinal rim
• Optic cup

These areas are particularly important because they contain nerve fibers that are damaged during glaucoma progression.

Results

Significant Improvements in Ocular Blood Flow

After four weeks of treatment, patients receiving Ginkgo biloba demonstrated increased blood flow in nearly every measured area surrounding the optic nerve.

Compared with placebo, statistically significant improvements in blood flow were observed in:

• Inferior nasal peripapillary retina
• Superior nasal neuroretinal rim
• Inferior nasal neuroretinal rim
• Superior temporal neuroretinal rim
• Inferior temporal neuroretinal rim
• Superior temporal peripapillary retina
• Inferior temporal peripapillary retina

These findings suggest that Ginkgo improved circulation in regions particularly vulnerable to glaucoma-related damage.

Blood Volume Also Improved

Blood volume increased throughout most measured regions.

Statistically significant improvements occurred in:

• Superior nasal neuroretinal rim
• Superior temporal neuroretinal rim

These areas represent important structural components of the optic nerve head.

Faster Blood Flow Velocity

Researchers also observed improvements in blood velocity.

Significant increases occurred in:

• Inferior temporal neuroretinal rim
• Superior temporal peripapillary retina

This suggests blood was not only present in greater amounts but was also moving more efficiently through certain regions.

No Significant Changes in Eye Pressure

Importantly, Ginkgo biloba did not significantly affect:

• Intraocular pressure (IOP)
• Mean deviation (MD)
• Corrected pattern standard deviation (CPSD)

These visual field measurements remained largely unchanged during the four-week study period.

Why Didn't Vision Improve?

At first glance, it may seem disappointing that visual field measurements did not improve.

However, glaucoma is a slowly progressive disease.

Researchers noted several reasons why vision improvements may not have been detected:

• The study lasted only four weeks
• Visual field testing was performed only once before and after treatment
• Structural and functional vision changes often require months or years to become measurable

The authors suggested that improved blood circulation may be an early biological effect that could eventually translate into visual benefits over a longer period.

Why These Findings Matter

This study is important because it addresses a growing area of glaucoma research: treatments that work independently of eye pressure.

The findings support the idea that glaucoma may involve both:

1. Mechanical damage from pressure
2. Vascular damage from impaired circulation

By improving blood flow around the optic nerve, Ginkgo biloba may help address a risk factor that conventional glaucoma medications often do not target.

Researchers also highlighted Ginkgo's potential neuroprotective effects. Laboratory studies suggest that Ginkgo may:

• Reduce oxidative stress
• Neutralize harmful free radicals
• Improve neuronal survival
• Protect retinal ganglion cells

Together, these vascular and neuroprotective properties make Ginkgo one of the most extensively studied natural compounds in glaucoma research.

Study Limitations

Although promising, the study has several limitations.

Small Sample Size

Only 30 patients participated.

Larger studies are needed to confirm the findings.

Short Duration

The study lasted just four weeks.

Researchers could not determine:

• Whether blood flow improvements persist long term
• Whether vision can be preserved over years
• Whether glaucoma progression can be slowed

Blood Flow Is a Surrogate Marker

The study demonstrated improved circulation, not direct prevention of vision loss.

Future studies must determine whether these blood flow changes ultimately improve clinical outcomes.

The Bottom Line

This randomized clinical trial found that four weeks of Ginkgo biloba supplementation significantly improved blood circulation around the optic nerve in patients with normal-tension glaucoma.

While the study did not demonstrate immediate improvements in visual field performance, the results provide important evidence supporting the vascular theory of glaucoma and suggest that improving ocular blood flow may be a valuable therapeutic target.

As researchers continue exploring treatments beyond eye pressure reduction, Ginkgo biloba remains one of the most promising natural compounds being investigated for glaucoma management.

Study Reference

Park JW, Kwon HJ, Chung WS, Kim CY, Seong GJ. Short-Term Effects of Ginkgo biloba Extract on Peripapillary Retinal Blood Flow in Normal Tension Glaucoma. Korean Journal of Ophthalmology. 2011;25(5):323-328. doi:10.3341/kjo.2011.25.5.323.