Electromagnetic stimulation for amblyopia: A systematic review of emerging techniques and their efficacy

Amblyopia, long considered untreatable in adults, may be responsive to Electromagnetic Stimulation (EMS) techniques to enhance neural plasticity. This systematic review evaluates the efficacy of EMS in treating adult amblyopia. A systematic literature review was conducted across online databases for prospective studies, clinical trials, or case series evaluating the effects of EMS on animal or human models of amblyopia. The primary outcomes of interest were visual acuity, contrast sensitivity, stereopsis, and visual evoked potentials. Of 34 initially identified studies, 20 met the inclusion criteria. Ten studies focused on transcranial direct current stimulation (tDCS), seven on repetitive transcranial magnetic stimulation (rTMS), and three on transcranial random noise stimulation (tRNS). tDCS studies demonstrated improvements in visual acuity, contrast sensitivity, and depth perception in human and animal models. rTMS studies showed positive outcomes in visual acuity and stereoacuity in adult amblyopes. tRNS studies reported improvements in visual acuity and contrast sensitivity in adults. Though current studies are limited by small sample sizes and brief follow-up durations, the observed enhancements in visual acuity, contrast sensitivity, and stereopsis across multiple studies signify that EMS has the potential to transform amblyopia treatment. These findings open new and exciting avenues for treating amblyopia beyond traditional critical periods.