Non-invasive brain stimulation for treating visual defects: a systematic review and meta-analysis

Abstract

Objective: We evaluated the efficacy of applying repetitive transorbital alternating current stimulation (rTACS) to patients suffering from visual defects, especially homonymous hemianopia.

Background: Stroke or optic neuropathy would result in vision loss or Visual field defect (VFD) and homonymous hemianopia. Recently, one of the commonly used procedures to relieve VFD is non-invasive brain stimulation (NIBS).

Methods: A comprehensive search covering publications in PubMed, Embase, Cochrane, and Scopus, spanning until September 2023 was performed. Relevant Randomized controlled trials (RCTs) were selected, and their data were extracted and analyzed. Pooled mean difference (MD) was calculated for change in the high-resolution perimetry detection accuracy (HRP DA) and fixation accuracy (HRP FA), static automated perimetry foveal threshold (SAP FT), and visual acuity (VA) of near vision outcomes.

Results: We pooled in our analysis 4 RCTs. Compared to the sham group, rTACS patients had a significantly higher HRP DA (SMD = 0.35; 95% CI [0.003,0.694] P = 0.048). However, the analysis did not favor any of the compared groups in HRP FA, SAP FT, VA of near vision, and mean threshold (SMD = 0.14; 95% CI [-0.21,0.48] P = 0.43], (SMD = 0.17; 95% CI [-0.11,0.45] P = 0.23), (SMD = 0.32; 95%CI [-0.24,0.88] P = 0.26), and (SMD = 0.31; 95% CI [-0.04,0.65] P = 0.08) respectively.

Conclusions: Current evidence suggests that rTACS exhibits a promising approach in homonymous hemianopia patients, where it significantly increased HRP DA. Despite the results' failure to attain statistical significance in some outcomes, it underscores the necessity for larger RCTs with longer follow-up periods.

Keywords: Brain stimulation; Fixation accuracy; Homonymous hemianopia; Visual field defect.