Non-invasive electrical brain stimulation for vision restoration after stroke: An exploratory randomized trial...

Area of Science:

• Neuroscience
• Ophthalmology
• Neurology

Background:

• Occipital strokes frequently result in permanent homonymous hemianopia, causing significant disability.
• Non-invasive electrical brain stimulation (NIBS) has previously shown promise in improving vision after optic nerve damage and post-stroke vision loss when combined with training.

Purpose of the Study:

• To investigate the efficacy of different non-invasive electrical brain stimulation (NIBS) modalities for the rehabilitation of homonymous hemianopia in patients with chronic stroke.

Main Methods:

• A randomized, double-blinded, sham-controlled trial involving 56 patients with homonymous hemianopia.
• Three experimental arms: i) repetitive transorbital alternating current stimulation (rtACS) vs. tDCS/rtACS vs. sham; ii) rtACS vs. sham; iii) tDCS of the visual cortex vs. sham.
• Visual functions were assessed pre-intervention, post-intervention, and after an 8-week follow-up, with visual field changes as the primary outcome.

Main Results:

• Experiments 1 and 2 (rtACS and tDCS/rtACS) did not yield significant primary outcome improvements compared to sham.
• Experiment 3 showed that tDCS of the visual cortex significantly increased the visual field of the contralesional eye compared to sham.
• tDCS/rtACS demonstrated improvements in dynamic vision, reading, and the contralesional eye's visual field, though not superior to other groups; rtACS alone improved foveal sensitivity but had limited overall effect.

Conclusions:

• This exploratory trial confirmed the safety of NIBS for stroke-related homonymous hemianopia but did not demonstrate a main effect on vision restoration.
• Transcranial direct current stimulation (tDCS) and combined tDCS/rtACS showed potential for improving visually guided performance, warranting further investigation in larger trials.