Effectiveness of tDCS in Paediatric Amblyopia.

Amblyopia is a neurodevelopmental visual disorder characterised by reduced visual performance despite optimal optical correction and the absence of ocular pathology. It affects up to 2-4% of children and is the leading cause of visual impairment in this population. Conventional treatment involves optical correction and patching of the contralateral (non-amblyopic) eye, which usually produces limited improvement, low therapeutic compliance and frequent relapses, highlighting the need for new approaches based on neuroplasticity.

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that can modify cortical excitability by regulating GABAergic inhibition in the primary visual cortex (V1). It has been safely used in children with attention deficit disorder, schizophrenia, epilepsy or cerebral palsy.

Preliminary data from our group show that after three sessions of tDCS on paediatric strabismic amblyopia, there are significant and sustained improvements in visual acuity, contrast sensitivity, and stereopsis at 3 months.

This project proposes a randomised, double-blind clinical trial to evaluate the efficacy, safety and optimal dosage regimen of tDCS in children aged 4 to 14 years with strabismic or anisometropic amblyopia classified as non-responsive to occlusion therapy, according to the criteria established by the Pediatric Eye Disease Investigation Group (PEDIG). Objective biomarkers will be included using electroencephalogram, visual evoked potentials (pattern) and functional magnetic resonance imaging to explore cortical functional and structural changes, together with biochemical assessment of GABA levels.

The expected outcome is to validate tDCS as an effective, rapid, and safe alternative or complementary therapy for amblyopia. Demonstrating sustained visual and cortical improvements would support its inclusion in paediatric clinical protocols and promote translational neuro-ophthalmological rehabilitation

Inclusion criteria

• Children aged 4-14 years.
• Strabismic amblyopia resistant to patching (PEDIG criteria).
• Anisometropic amblyopia resistant to patching (PEDIG criteria).

Exclusion criteria

• Ocular pathology.
• Nystagmus.
• Mental disability.
• Cognitive delay.
• Neurological problems incompatible with treatment.
• Pacemakers.
• Intracranial electrodes.
• Implanted defibrillators.
• Cranial pathologies.
• Cranial lesions.
• Withdrawal will occur upon adverse events, protocol deviation, refusal, or loss to follow-up.