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Review: Potential Role of Ginkgo Biloba in Glaucoma

Ginkgo Biloba Review: Potential Role in Glaucoma

Treatment of glaucoma largely focuses on lowering intraocular pressure (IOP), a major risk factor for progressive glaucomatous optic nerve damage. However, it is clear that IOP is just one of many factors contributing to the pathophysiology of glaucoma. In addition to elevated IOP, vascular dysfunction, mitochondrial dysfunction and oxidative stress have been posited as mechanisms of glaucomatous damage.

According to the authors of a new review on the effect of Ginkgo biloba extract in glaucoma patients (1), physicians, researchers and patients have explored complementary approaches to traditional glaucoma treatment, including the use of antioxidants and botanicals. Since as many as 5-10% of glaucoma patients report use of such strategies, it is important for clinicians to be knowledgeable about the research and literature on complementary and alternative medicine (CAM) therapies, wrote the authors from the University of California, San Francisco (UCSF), Department of Ophthalmology and the UCSF Koret Vision Center.

Results. The paper, which includes a summary of standardized Ginkgo biloba (GBE) pharmacology, indicates that published clinical studies to date evaluating the effect of GBE in ocular vasculature support the ability of GBE to increase ocular blood flow. The authors describe the most recently published investigation, a controlled cross-over trial of 45 patients with OAG which examined the effects of GBE and antioxidants on ocular blood flow (2).

Data from animal models suggest that GBE may have a neuro-protective effect on retinal ganglion cells. However, the clinical effect of GBE on glaucoma outcomes such as visual field performance remains inconclusive.

Safety. In terms of safety, the authors conclude that GE is well tolerated with a low side effect profile. Several systematic reviews report no difference in side effects with GBE compared with placebo at doses ranging from 80-600 mg daily for at least 22 weeks. There have been some concerns regarding the bleeding risk while on ginkgo supplementation, particularly when used with aspirin. A systematic review of case reports of bleeding associated with ginkgo showed that out of 15 cases, 13 had other risk factors for bleeding and three cases reported increased bleeding times. Other studies looking at the concurrent use of GBE and aspirin found no difference in bleeding time, platelet function or coagulation parameters, compared with aspirin alone.

A recently published randomized controlled trial (6-month duration, 348 patients), lends credence to those findings (3). GBE (400 mg daily) combined with aspirin (100 mg daily) alleviated cognitive and neurological deficits after acute ischemic stroke more effectively than did aspirin alone, without increasing the incidence of vascular or adverse events.

Future Directions. The authors of this review point out that studies published on GBE and ocular blood flow have utilized color Doppler imaging (CDI), or confocal scanning laser Doppler flowmetry (CSLDF) imaging techniques, or both. Although CDI is a useful method to evaluate larger retrobulbar ocular blood vessels, it cannot provide information on retinal vasculature. CSLDF does provide information on retinal vasculature, but this technique may be sensitive to changes in illumination and eye movement. A future direction in studying the effects of GBE in glaucoma is to employ imaging techniques such as optical coherence tomography angiography (OCT-A).

Conclusion. Larger clinical studies are necessary to establish the clinical benefit of GBE with or without antioxidants in normal and high-tension glaucoma patients. For clinicians whose patients do use GBE-containing supplements, current evidence supports the safety of GBE and its apparent ability to increase ocular blood flow. The important caveat is that patients understand that GBE cannot displace or replace the use of other interventions known to preserve the visual field.

References

1. Kang JM and Lin S. Ginkgo biloba and its potential role in glaucoma. Curr Opin Ophthalmol. 9(2):116-120, 2018.
2. Harris A, et al. The effects of antioxidants on ocular blood flow in patients with glaucoma. Acta Ophthalmol. [Epub ahead of print] 2017.
3. Li S, et al Ginkgo biloba extract improved cognitive and neurological functions of acute ischaemic stroke: a randomized controlled trial. Stroke and Vascular Neurology 2017; svn-2017-000104.