What is Glaucoma?
Glaucoma is a disease of the optic nerve and is the leading cause of irreversible blindness worldwide. This condition is characterized by a particular pattern of progressive damage to the optic nerve that generally begins with a subtle loss of side vision (peripheral vision). If glaucoma is not diagnosed and treated, it can progress to loss of central vision and blindness. Glaucoma is usually, but not always, associated with elevated pressure in the eye (intraocular pressure). Generally, it is this elevated eye pressure that leads to damage of the eye (optic) nerve. In some cases, glaucoma may occur in the presence of normal eye pressure. This form of glaucoma is called “normal tension glaucoma” (NTG) and is usually associated with poor regulation of blood flow to the optic nerve.
How Common is Glaucoma?
Currently more than 6 million individuals are blind in both eyes from this condition. It is estimated that over 3 million people have glaucoma in the United States. However, as many as half of the individuals with glaucoma may not know they have the disease. The reason they are unaware is that glaucoma initially causes no symptoms, and the subsequent loss of side vision (peripheral vision) is usually not recognized.
Why Ginkgo Biloba?
It has long been known that ginkgo biloba improves blood circulation, presumably by reducing the tendency of blood to clot and thus helps maintain blood flow to sensitive tissues, such as the brain and optic nerve. Improved blood flow to these organs may ease the course of glaucoma.
Researchers recruited 27 patients between the ages of 58 and 80 for a clinical trial. Each patient had Normal Tension Glaucoma in each eye and reported progressive loss of vision over time. The patients were randomly divided into two groups in a crossover design. One group received 40 mg of a typical ginkgo biloba extract three times daily for 4 weeks, followed by a washout period (no treatment) of 8 weeks, followed by placebo for an additional 4 weeks. The other group received the same treatment in the reverse order. Standard measurements to determine the extent of visual field loss were recorded in each phase of the trial.*
As expected, the placebo had no impact on the visual performance. However, when the NTG patients in either group were treated with the ginkgo extract, each measurement of visual field showed significant improvement. Additionally, researchers noted the visual benefit was lost following cessation of the ginkgo biloba treatment. That is, during the washout period, visual field performance returned to baseline levels, indicating that ginkgo biloba must be continually consumed in order to produce clinical benefits.*
Ginkgo biloba extract has several properties that might have contributed to the beneficial effects observed in this trial. Its antioxidant activity might have protected the optic nerve from oxidative damage, and its ability to increase blood flow and oxygen utilization might have protected the optic nerve from damage due to lack of oxygen. Furthermore, its ability to increase blood flow to the brain might have improved eye sensitivity, resulting in improved visual function.*
*Source: Ophthalmology. 2003 Feb;110(2):359-62