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Ginkgo biloba has been used in Chinese traditional medicine since 3000 BC for treating various afflictions from asthma to vascular disease. Natural ginkgolides inhibit platelet activating factor (PAF) by binding to its membrane receptor. Inhibition of PAF by Ginkgo biloba has been shown to increase skin perfusion and decrease blood viscosity. Wimpissinger et al. (695) have investigated the effects of Ginkgo biloba extract on retinal blood flow in healthy male volunteers. The authors have utilized several imaging technologies to assess ocular blood flow, mostly sampling within the retinal circulation. No significant effects on retinal perfusion were found during a three-hour window post ingestion when compared to placebo.
Due to the widespread popularity and use of over-the-counter medical supplements, it is important that we understand the effects of such agents as Ginkgo biloba on ocular circulationOne strong point of this investigation was the use of multiple imaging technologies to investigate the ocular circulation. Too often a study will conclude ocular blood flow is unaffected by a medication while using only one imaging technique or sampling in only one ocular tissue bed. The utilization of all healthy male volunteers is an obvious limitation for this study which the authors hint towards in their conclusion. The intact healthy vascular autoregulatory ability of these subjects would likely absorb and damper any physiochemical influence of Ginkgo biloba extract within the retina. It is also possible that ocular hemodynamic changes may have occurred in choroidal tissue or within the retrobulbar blood vessels which were not directly measured during this investigation. Other studies have reported Ginkgo biloba increases blood flow velocities in the ophthalmic artery of healthy subjects.
Due to the widespread popularity and use of over-the-counter medical supplements such as Ginkgo biloba it is imperative that we understand the effects of these medications on ocular circulation. Future Ginkgo biloba blood flow research should utilize longitudinal studies and subjects with compromised ocular perfusion, including glaucoma patients.