As a neurodevelopmental visual disorder, amblyopia, especially monocular form-deprivation amblyopia, can lead to severe visual developmental impairments. Due to reduced neural plasticity in the visual cortex after the critical period of visual development, older children and adults with amblyopia show poor responses to conventional treatments, lacking effective therapeutic options. Recent basic and clinical research has shown that transcranial direct current stimulation can effectively treat adult amblyopia by altering cortical excitability, enhancing synaptic plasticity, and affecting the excitatory/inhibitory balance in the cortex to reboot adult visual cortex plasticity. This proposed study aims to conduct a large-scale prospective randomized controlled trial to objectively assess the efficacy and safety of transcranial direct current stimulation in treating amblyopia in older adolescents and adults. By comparing changes in best-corrected visual acuity, visual evoked potentials(VEPs), contrast sensitivity, and functional connectivity between the visual cortex and other cortical areas using fMRI, the study seeks to provide robust clinical evidence, clarify the treatment effects of transcranial direct current stimulation in adult amblyopia, elucidate potential mechanisms of enhancing adult visual cortex plasticity with transcranial direct current stimulation, and potentially offer a safe and effective treatment modality for adult amblyopia.