To Evaluate the Effect of Ginkgo Biloba Extract on Optic Nerve Head Perfusion Examined Using OCTA

Inclusion Criteria: * 18 years of age or older * Early open angle glaucoma based on gonioscopy, clinical assessment of optic nerve head, OCT optic nerve and Humphrey Visual Field 24-2 (MD \< -10dB) and positive Glaucoma Hemifield Test * BCVA equal or better than 6/12 * Written consent * Ability to comply with treatment intervention for duration of study Exclusion Criteria: * Younger than 18 years of age * Angle closure glaucoma or secondary open angle glaucoma * Refraction exceeding 6D spherical equivalent or 3D astigmatism * Severe corneal, lens, vitreous media opacity limit signal strength of OCTA imaging * Severe open angle glaucoma with visual field mean deviation worse than -10dB * Inability to comply to treatment intervention (e.g. swallowing difficulty) * History of ocular disease affecting ocular perfusion (e.g. CRAO, CRVO, diabetic retinopathy, ocular ischemic syndrome, ischemic optic neuropathy) * History of glaucoma surgery * Those taking anticoagulant therapy * Those with blood disorders or diabetes * Women who were pregnant, planning to become pregnant, or who were breast-feeding, * Patients with a history of seizures or who were currently taking anti-convulsant medication, and * Taking any drugs that may interact with GBE