Glaucoma Rehabilitation Using ElectricAI Transcranial Stimulation (GREAT) - Randomized Controlled Trial Using Combined Perceptual Learning and Transcranial Electrical Stimulation for Vision Enhancement

Inclusion Criteria: * Age range from 18 to 80 years; * Diagnosis of primary open angle or normal tension glaucoma with relative scotoma in both eyes; * A relative scotoma defined as a Humphrey Field Analyser (HFA) threshold perimetry loss (mean deviation of -6dB) within the central 24 degree of the visual field for at least one eye; * Best-corrected distance visual acuity of 6/12 or better (equivalent to 0.3 logMAR acuity or better to confirm that participant's central vision is preserved). * Stable vision and visual field loss for at least 3 months; * With a cognitive functional score of 22 or above in the Montreal Cognitive Assessment - Hong Kong version (HK-MoCA) (to confirm participant's intact cognitive function). Exclusion Criteria: * Ocular diseases other than glaucoma (e.g. age-related macular degeneration, diabetic retinopathy, moderate to severe cataract) or severe hearing impairment (to ensure that participant can hear the instructions clearly during assessments and training); * Severe medical problems (e.g. stroke, Parkinson's disease) or self-reported neurological (e.g. brain surgery, brain tumor, peripheral neuropathy), or cognitive disorders (e.g. diagnosed dementia or cognitive impairment); * Self-reported vestibular or cerebellar dysfunction, history of vertigo; * Using any medications for any neurological conditions or psychiatric drugs (e.g. sedative, hypnotic) that might interfere motor control; * Contraindications for non-invasive brain stimulation.