Non-invasive electrical brain stimulation induces vision restoration in patients with visual pathway damage

Abstract

Dear Editor, Non-invasive electrical stimulation may diminish functional deficits of visual perception. This concerns not only the application of transcorneal electrical stimulation (TES) in patients with retinal and optic nerve disease as reported by Gekeler and Bartz-Schmidt [1] but also non-invasive transorbital alternating current stimulation (ACS). Basic stimulation parameters of TES and transorbital ACS are similar since in both approaches current intensity is individually adjusted according to how well patients perceived phosphenes. TES evidence was obtained in a recent randomized study with patients suffering from retinitis pigmentosa [2]. Here, we wish to add further aspects that were not considered by Gekeler and Bartz-Schmidt. Firstly, non-invasive electrical stimulation has shown therapeutic efficacy in diminishing functional deficits of visual perception in patients with optic nerve disease when non-invasive transorbital ACS is applied [3–6]. Second, visual cortex excitability and related performance changes induced by transcranial direct current stimulation (tDCS) indicate that visual system functions can be altered by non-invasive currents [7].