Abstract
BackgroundVision loss after optic neuropathy is considered irreversible. Here, repetitive transorbital alternating current stimulation (rtACS) was applied in partially blind patients with the goal of activating their residual vision.MethodsWe conducted a multicenter, prospective, randomized, double-blind, sham-controlled trial in an ambulatory setting with daily application of rtACS (n = 45) or sham-stimulation (n = 37) for 50 min for a duration of 10 week days. A volunteer sample of patients with optic nerve damage (mean age 59.1 yrs) was recruited. The primary outcome measure for efficacy was super-threshold visual fields with 48 hrs after the last treatment day and at 2-months follow-up. Secondary outcome measures were near-threshold visual fields, reaction time, visual acuity, and resting-state EEGs to assess changes in brain physiology.ResultsThe rtACS-treated group had a mean improvement in visual field of 24.0% which was significantly greater than after sham-stimulation (2.5%). This improvement persisted for at least 2 months in terms of both within- and between-group comparisons. Secondary analyses revealed improvements of near-threshold visual fields in the central 5° and increased thresholds in static perimetry after rtACS and improved reaction times, but visual acuity did not change compared to shams. Visual field improvement induced by rtACS was associated with EEG power-spectra and coherence alterations in visual cortical networks which are interpreted as signs of neuromodulation. Current flow simulation indicates current in the frontal cortex, eye, and optic nerve and in the subcortical but not in the cortical regions.ConclusionrtACS treatment is a safe and effective means to partially restore vision after optic nerve damage probably by modulating brain plasticity. This class 1 evidence suggests that visual fields can be improved in a clinically meaningful way.Trial RegistrationClinicalTrials.gov NCT01280877
Highlights
Optic neuropathy and glaucoma are frequent causes of chronic blindness [1]
The repetitive transorbital alternating current stimulation (rtACS)-treated group had a mean improvement in visual field of 24.0% which was significantly greater than after sham-stimulation (2.5%)
Secondary analyses revealed improvements of near-threshold visual fields in the central 5° and increased thresholds in static perimetry after rtACS and improved reaction times, but visual acuity did not change compared to shams
Summary
Optic neuropathy and glaucoma are frequent causes of chronic blindness [1]. Exploratory evidence indicates that ACS can enhance neuronal function both in normal subjects [8,9] and in patients with VF loss who still have some residual vision [10]. The proposed mechanism of action is neuromodulation of oscillatory brain activity towards a more synchronized EEG via entrainment of specific stimulation frequencies [10,11], and the reorganization of brain functional connectivity networks [12] is considered to be a novel and promising avenue for visual rehabilitation [13]. Vision loss after optic neuropathy is considered irreversible. Repetitive transorbital alternating current stimulation (rtACS) was applied in partially blind patients with the goal of activating their residual vision
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