By Prof. Raphael Nyarkotey OBU
Quaranta et al.(2003) found evidence that Ginkgo biloba may have a benefit in the treatment of glaucoma. Patients with Normal Tension Glaucoma (NGT) who were given 40mg of Ginkgo biloba extract three times a day (120mg total daily dose) showed a short-term improvement in their visual fields compared to those who took the placebo.
Glaucoma includes several forms of eye disease that cause damage to the structures within the eye by the pressure of the fluid within the globe. The particular form of glaucoma that ginkgo biloba extract is used to treat is called low-tension glaucoma when the eye sustains damage even though the internal pressure is within the normal range.
Usually, ‘intraocular pressure (IOP)’ in glaucoma is elevated, and does damage to the retinal nerve fibre layer and the head of the optic nerve, causing vision loss. This type of glaucoma is called ‘primary open-angle glaucoma (POAG)’ and is the most common type, causing loss of vision without symptoms, at least in the early stages. In this disease, medications are prescribed to lower IOP into the normal range, where the eye does not sustain damage.
POAG does its damage by both direct pressure on the tissues of the retina and optic nerve and by restricting circulation within the eye. If the IOP is too high, the normal blood pressure is unable to overcome it and circulation of nutrients to the retina through the blood vessels is compromised. Conventional treatment using medications to reduce IOP does not help people with low-tension glaucoma, as IOP is already low.
It is not known why some eyes are damaged even by relatively low IOP, but GBE is thought to increase blood flow to the eye. Only calcium blockers are currently available for such treatment, but these have not been widely accepted.
Improved circulation with ginkgo extract works to prevent damage from even low-tension glaucoma and is also thought to have beneficial effects on circulation elsewhere, such as the brain in dementias or the feet in diabetes, as well as preserve vision from both diabetic retinopathy and age-related macular degeneration, two other causes of major vision loss.
Gingko biloba also has anti-oxidant activity that may be beneficial to prevent damage to the optic nerve. Also, elevated blood flow to the brain may increase the sensitivity of the eyes, resulting in improved visual function; some studies indicate that this may be the mechanism by which Gingko Biloba may be helpful in macular degeneration (kanataoptometry.ca).
Gingko Biloba
Gingko Biloba is a tree native to China but also found in Japan and Korea. Its fan-shaped leaves contain a complex combination of chemicals, including flavonoid glycosides and terpenoids. Pharmacologically, these can affect many processes in the body, including influencing neurotransmitters in the brain and improving blood flow by reducing the action of platelets.
Studies on Glaucoma
Emerging studies have reported promising benefits of ginkgo to vision and eye health. One review study (Kang and Lin. 2018) showed that people with glaucoma who supplemented with ginkgo experienced increased blood flow to the eye; however, it doesn’t mean better vision.
Earlier review (Evans JR. 2013) evaluated two studies on the effect of ginkgo extract on the progression of age-related macular degeneration. Some participants reported an improvement in vision, but this wasn’t statistically significant across the board. Many of these positive results seem to be related to increased blood flow to the eye.
An earlier human study by Russo et al.(2009) investigated the clinical efficacy of a Ginkgo biloba extract associated with hyaluronic acid ophthalmic solution (GB-HA, Trium, SOOFT, Italy), compared to hyaluronic acid ophthalmic solution (HA) alone, in seasonal allergic conjunctivitis (AC) in a total of 60 patients for a washout period of 15 days.
The study found that compared to placebo eye drops, the drops with ginkgo biloba extract reduced the symptoms of pink eye caused by allergies. Another human study (Lee et al. 2013) also evaluated the long-term effect of Ginkgo biloba extract (GBE) on the progression of visual field (VF) defects in patients with normal tension glaucoma (NTG).
In this study, 42 eyes of 42 patients with treated NTG who received 80mg GBE 2 times daily and who had at least 5 VF tests using the Humphrey Visual Field Analyzer for more than 4 years before and after GBE treatment were evaluated in this retrospective study. The mean follow-up period was 12.3 years. The study concluded that ginkgo biloba extract administration slowed the progression of visual field damage in patients with NTG, especially in zone 1, corresponding to the superior central field.
Another review (Cybulska-Heinrich et al. 2012) also suggests that ginkgo biloba positively influences oxidative stress and disturbed vascular circulation. Both reduced microcirculation and oxidative stress are involved in the pathogenesis of glaucoma. Therefore, already from a theoretical point of view, the pharmacological properties of ginkgo can be expected to be beneficial for the eye as well.
They recommend that ginkgo would probably be beneficial for all glaucoma patients. However, the use of ginkgo can be recommended as an adjuvant therapy only for normal tension glaucoma patients and for high-tension glaucoma patients. Another review by (Quaranta et al. 2014) strongly supports that Gingko biloba induces an improvement in visual field damage.
Harris et al. (2018) trial also found improvement in blood microcirculation to the optic nerve and oxidative stress in the bloodstream. The study further found that a ginkgo biloba blend with other antioxidants and omega-3 fatty acids (Optic Nerve Formula) taken 2 capsules twice daily for 1 month, produced significant improvement in blood flow to the retina and optic nerve.
A recent human study (Elwahidy et al. 2022) compared timolol eye drop and ginkgo biloba safety and efficacy in moderate POAG. Primary open-angle glaucoma (POAG), is a chronic, progressive neurodegenerative disease characterised by cupping of the optic disc and loss of visual field. The study used ‘90 eyes’ with moderate POAG with a dose of 120mg/day of gingko to a daily dose of Timolol and a control group of ‘90 eyes’ continued on Timolol only for 6 months. The study concluded that ginkgo biloba is a beneficial adjuvant to Timolol in moderate POAG.
Recommended dosage
Ginkgo biloba extract may be found in many dosages. The dosage used in the afore-mentioned studies ranged from 40mg taken three times daily (120mg total daily dose) to 80mg twice daily (160mg total daily dose).
Mechanism of action
Various studies in vivo (in animal studies) and in vitro (in the laboratory) models have shown that ginkgo biloba extract (GBE) has neuroprotective effects. Different studies have shown that ginkgo biloba extracts may have the following potential benefits:
- Improved blood flow to the optic nerve
- Neuroprotective effects
- Antioxidant effect
- Anti-inflammatory action
Due to their perceived antioxidant, anti-inflammatory and neuroprotective benefits, various flavonoids (and in particular GBE) have been proposed for the treatment of non-pressure-dependent risk factors associated with glaucoma.
Take home
Glaucoma Australia.Org agreed that there is evidence both in animal models and in humans that Ginkgo is a beneficial treatment for glaucoma. Examples of such evidence include increased survival of rat retinal ganglion cells in culture when exposed to Ginkgo and improvement in the visual field scores of patients with glaucoma after a course of treatment with ginkgo biloba extract. The mechanism behind such apparent benefits is not certain; improved blood supply to the eye (including the optic nerve) has been demonstrated and may be important.
Ginkgo is generally safe and well-tolerated. As it can increase bleeding, it should be used with caution in individuals taking anticoagulants or in those with medical conditions associated with increased bleeding such as haemophilia, chronic liver disease or thrombocytopaenia.
It is important to appreciate that the benefit of ginkgo for preventing glaucoma onset or progression is much less certain than other strategies such as lowering intraocular pressure. The latter has been extensively studied with consistent results whereas research of gingko is much more limited. Currently, ginkgo is indicated for glaucoma management in eyes where progression is detected despite low intra-ocular pressures.
>>>NB: Prof. Nyarkotey has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions and medical associations to justify his write-ups. My articles are for educational purposes and do not serve as medical advice for treatment. I aim to educate the public about evidence-based scientific naturopathic therapies.
>>>The writer is a Professor of Naturopathic Healthcare, a Medical Journalist and a science writer. He is also President, Nyarkotey University College of Holistic Medicine & Technology (NUCHMT)/African Naturopathic Foundation, Ashaiman, Ghana.
- mail: [email protected]. Visit profnyarkotey.com for more.
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References
- Kang JM, Lin S. Ginkgo biloba and its potential role in glaucoma. Curr Opin Ophthalmol. 2018 Mar;29(2):116-120. doi: 10.1097/ICU.0000000000000459. PMID: 29206653.
- Evans JR. Ginkgo biloba extract for age-related macular degeneration. Cochrane Database Syst Rev. 2013 Jan 31;2013(1):CD001775. doi: 10.1002/14651858.CD001775.pub2. PMID: 23440785; PMCID: PMC7061350.
- Russo V, Stella A, Appezzati L, Barone A, Stagni E, Roszkowska A, Delle Noci N. Clinical efficacy of a Ginkgo biloba extract in the topical treatment of allergic conjunctivitis. Eur J Ophthalmol. 2009 May-Jun;19(3):331-6. doi: 10.1177/112067210901900301. PMID: 19396774.
- Cybulska-Heinrich AK, Mozaffarieh M, Flammer J. Ginkgo biloba: an adjuvant therapy for progressive normal and high tension glaucoma. Mol Vis. 2012;18:390-402. Epub 2012 Feb 9. PMID: 22355250; PMCID: PMC3283204.
- Harris A, Gross J, Moore N, Do T, Huang A, Gama W, Siesky B. The effects of antioxidants on ocular blood flow in patients with glaucoma. Acta Ophthalmol. 2018 Mar;96(2):e237-e241. doi: 10.1111/aos.13530. Epub 2017 Aug 3. PMID: 28772005.
