Clinical Treatment of Transcranial Direct Current Stimulation in Older Adolescents With Amblyopia

Efficacy of Transcranial Direct Current Stimulation in the Amblyopia Treatment of Older Adolescents: A Cohort Study

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.

1. A prospective cohort study designed to evaluate the effectiveness of transcranial direct current stimulation (tDCS) in improving visual outcomes in older adolescents with amblyopia. Anodal tDCS Group: Participants will receive anodal transcranial direct current stimulation (tDCS) with electrodes placed over the occipital cortex, chosen due to its critical role in processing visual information and its potential responsiveness to neuromodulation in amblyopia treatment. The stimulation will be set at 0.1 mA for 20 minutes per session, twice a week, over 6 months; Sham Stimulation Group: Participants will receive sham tDCS with electrodes similarly placed over the occipital cortex. The stimulation will be set at 0 mA for 20 minutes per session, twice a week, over 6 months.
2. The impact of transcranial direct current stimulation on adult visual cortex plasticity and cortical functional assessment. Before and after transcranial direct current stimulation, resting-state and task-based functional magnetic resonance imaging (fMRI) are used to assess the functional activity between the visual cortex and other cortical regions. This evaluation aims to identify changes in adult visual cortex plasticity.

Inclusion Criteria:

• Children and their legal guardians have obtained consent in writing.
• Participants aged 10-30, of any gender.
• Participants must meet the diagnostic criteria for amblyopia: unilateral amblyopia with a difference of two lines or more in visual acuity between the eyes, or bilateral amblyopia with best-corrected visual acuity worse than 20/30 (or worse than 0.2 logMAR). The visual acuity charts to be used are LEA SYMBOLS® (Good-Lite Co., Elgin, IL) or HOTV visual acuity chart.

Exclusion Criteria:

• Participants who may have eye diseases affecting vision or refractive errors (such as cataracts, crystalline lens damage, glaucoma, macular degeneration, corneal disorders, retinitis pigmentosa, retinal detachment, severe vitreous opacities, etc
• History of eye trauma or intraocular surgery
• Inability to cooperate with examinations
• Presence of concomitant systemic diseases (such as epilepsy)
• Participation in any other experimental treatment within the past 3 months
• Other situations deemed unsuitable by the investigator.