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