Could Ginkgo Biloba Help Protect Vision in Normal-Tension Glaucoma? A Landmark Study Suggests It Might

Summary

For people living with normal-tension glaucoma—a form of glaucoma that damages vision even when eye pressure remains normal—the search for treatments beyond eye-pressure lowering has long been a challenge. A clinical trial published in Ophthalmology found that supplementation with Ginkgo biloba extract was associated with significant improvements in visual field performance among patients with established vision loss.

While the study was small and short-term, it remains one of the most frequently cited investigations examining whether improved blood flow and neuroprotection could benefit glaucoma patients.

Key Takeaways

• A randomized, placebo-controlled clinical trial evaluated Ginkgo biloba extract in patients with normal-tension glaucoma (NTG).
• Twenty-seven patients with progressive visual field loss participated.
• Patients taking Ginkgo biloba experienced statistically significant improvements in visual field measurements.
• No significant changes occurred in eye pressure, blood pressure, or heart rate.
• No serious ocular or systemic side effects were reported during the study.
• Researchers believe improved blood flow to the optic nerve and possible neuroprotective effects may explain the findings.
• Larger and longer-term studies are still needed before Ginkgo biloba can be recommended as a standard glaucoma treatment.

Why Is This Study Important?

When most people think about glaucoma, they think about elevated eye pressure damaging the optic nerve. However, normal-tension glaucoma (NTG) presents a puzzling exception.

In NTG, patients develop progressive optic nerve damage and vision loss despite having eye pressures within the normal range. This suggests that factors other than pressure may contribute to the disease.

Researchers have increasingly focused on:

• Reduced blood flow to the optic nerve
• Vascular dysfunction
• Oxidative stress
• Neurodegeneration
• Impaired blood vessel regulation

Because Ginkgo biloba extract has been shown to improve circulation, reduce oxidative damage, and potentially protect nerve cells, investigators wondered whether it could help preserve visual function in NTG patients.

This study was among the first rigorous clinical trials designed to test that hypothesis.

What Is Ginkgo Biloba?

Ginkgo biloba is an herbal extract derived from the leaves of the ancient Ginkgo tree, one of the oldest surviving tree species on Earth.

The standardized extract used in medical research contains biologically active compounds including:

• Flavonoids
• Terpene lactones
• Ginkgolides
• Bilobalide

Previous studies have suggested that Ginkgo biloba may:

• Improve blood circulation
• Reduce blood viscosity
• Increase tolerance of nerve cells to oxygen deprivation
• Act as an antioxidant
• Protect cell membranes from free-radical damage

These properties make it an intriguing candidate for diseases involving impaired blood flow and nerve damage.

Study Design

Type of Study

The investigators conducted a:

• Prospective study
• Randomized trial
• Placebo-controlled trial
• Double-masked (double-blind) trial
• Cross-over study

This design is considered one of the strongest methods for evaluating treatment effectiveness because each participant effectively serves as their own control.

Who Participated?

The study enrolled:

• 27 patients
• Average age: 70 years
• 11 men and 16 women
• All had bilateral normal-tension glaucoma
• All demonstrated progressive visual field deterioration

Importantly, participants had normal eye pressures (18 mmHg or lower) and evidence of ongoing glaucoma progression despite those normal pressures.

Treatment Protocol

Participants were randomly assigned to one of two treatment sequences:

Group A

• Ginkgo biloba extract for 4 weeks
• 8-week washout period
• Placebo for 4 weeks

Group B

• Placebo for 4 weeks
• 8-week washout period
• Ginkgo biloba extract for 4 weeks

The Ginkgo dose was:

40 mg taken three times daily (120 mg/day total)

The placebo capsules looked identical and contained fructose.

Neither patients nor investigators knew which treatment was being administered during each phase.

How Did Researchers Measure Improvement?

Visual Field Testing

The primary outcome was visual field performance.

Visual fields measure how much of the surrounding environment a person can see while looking straight ahead. Glaucoma typically causes gradual loss of peripheral vision before affecting central vision.

Researchers used the Humphrey Visual Field Analyzer, one of the most widely used glaucoma testing systems worldwide.

Understanding Mean Deviation (MD)

Mean Deviation (MD) measures overall visual field loss compared with healthy individuals of the same age.

• More negative values indicate greater visual field damage.
• Improvement means the value moves closer to normal.

Think of MD as a summary score reflecting the overall health of a patient's visual field.

Understanding Corrected Pattern Standard Deviation (CPSD)

Corrected Pattern Standard Deviation (CPSD) measures localized visual field defects.

Higher CPSD values generally indicate more irregular and severe visual field abnormalities.

Lower CPSD values suggest improved visual field function.

Together, MD and CPSD provide a comprehensive assessment of glaucoma-related vision loss.

Results

Significant Improvement After Ginkgo Biloba

When researchers combined results from all participants, they observed significant improvements after Ginkgo treatment.

Mean Deviation (MD)

• Baseline: 11.40 dB
• After Ginkgo biloba: 8.78 dB

Statistically significant improvement (P < 0.0001)

Corrected Pattern Standard Deviation (CPSD)

• Baseline: 10.93 dB
• After Ginkgo biloba: 8.13 dB

Statistically significant improvement (P < 0.0001)

Notably, these improvements occurred regardless of whether patients received Ginkgo first or placebo first.

Placebo Did Not Produce Similar Benefits

Patients receiving placebo showed no meaningful changes in visual field measurements.

This finding strengthens the possibility that the observed benefits were related to Ginkgo biloba rather than random variation or a learning effect from repeated testing.

No Changes in Eye Pressure

One of the most interesting findings was that Ginkgo biloba did not lower intraocular pressure.

Researchers observed no significant changes in:

• Eye pressure
• Blood pressure
• Heart rate

This suggests any visual benefits may have occurred through mechanisms unrelated to pressure reduction.

Safety Findings

The treatment was well tolerated.

Researchers reported:

• No ocular side effects
• No systemic side effects
• No serious adverse events

However, because treatment lasted only four weeks, long-term safety could not be fully evaluated.

Why Might Ginkgo Biloba Help?

The researchers proposed several possible explanations.

Improved Optic Nerve Blood Flow

Previous studies have shown that Ginkgo biloba can increase blood flow in the ophthalmic artery, the vessel supplying blood to the eye.

Better circulation may improve oxygen and nutrient delivery to vulnerable optic nerve tissues.

Antioxidant Protection

Oxidative stress is increasingly recognized as a contributor to optic nerve damage.

Ginkgo's antioxidant compounds may help neutralize free radicals and reduce cellular injury.

Neuroprotective Effects

Perhaps most intriguing is Ginkgo's potential neuroprotective action.

Laboratory studies suggest Ginkgo may:

• Increase neuronal resistance to oxygen deprivation
• Support neurotransmitter function
• Protect nerve cell membranes

If confirmed, these effects could help preserve retinal ganglion cells—the neurons that die in glaucoma.

What Are the Limitations of This Study?

Despite the promising results, several limitations deserve attention.

Small Sample Size

Only 27 patients participated.

Small studies can sometimes overestimate treatment benefits.

Short Duration

Each treatment phase lasted only four weeks.

Researchers could not determine:

• Whether benefits persist long term
• Whether progression of glaucoma slows over years
• Whether permanent vision preservation occurs

Functional Improvement vs. Disease Modification

The study showed improvement in visual field measurements, but it did not prove that Ginkgo biloba prevents optic nerve damage or alters the underlying disease process.

Future studies would need imaging and long-term follow-up to answer that question.

What Does This Mean for Glaucoma Patients Today?

More than two decades after publication, this study remains an important piece of evidence supporting further investigation of Ginkgo biloba in normal-tension glaucoma.

The findings suggest that glaucoma treatment may eventually involve more than simply lowering eye pressure. Improving blood flow, reducing oxidative stress, and protecting nerve cells could become complementary therapeutic strategies.

However, patients should not interpret this study as proof that Ginkgo biloba can replace conventional glaucoma treatment. Eye-pressure control remains the only approach definitively proven to reduce glaucoma progression.

Anyone considering Ginkgo supplementation should discuss it with their ophthalmologist, especially because Ginkgo may interact with blood-thinning medications and other treatments.

Study Reference

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(2):359–364. doi:10.1016/S0161-6420(02)01745-1.