Background: Through transcranial magnetic stimulation (TMS) it is possible to change cortical excitability of the visual cortex, and to influence binocular balance. The main goal of our study is to assess the effect of transcranial magnetic stimulation, specifically theta burst stimulation (TBS), in a group of amblyopic volunteers measuring several visual parameters: visual acuity, suppressive imbalance, and stereoacuity. Methods: Thirteen volunteers aged 19 to 24 years, randomly split in 2 groups, underwent 1 session of continuous TBS, stimulating the right occipital lobe. The first group with 8 volunteers was exposed to active stimulation with cTBS, and the other group with 5 volunteers was exposed to placebo stimulation. Results: Significant improvements in visual acuity, suppressive imbalance, and stereoacuity were found in the amblyopic eye after cTBS. The average value of amblyopia in visual acuity before stimulation was 0.32 ± 0.20 logMar and after cTBS was 0.19 ± 0.17 logMar. The mean value for the control group before placebo stimulation was 0.28 ± 0.17 and after placebo stimulation was 0.28 ± 0.16. The suppressive imbalance in the group of amblyope subjects stimulated before cTBS was 0.26 ± 0.18 and after was 0.12 ± 0.12; the suppressive imbalance of the control group before the placebo stimulation was 0.34 ± 0.37 and after was 0.32 ± 0.40. Conclusions: Visual acuity, suppressive imbalance, and stereoacuity had significant enhancements compared with baseline after cTBS over the right occipital lobe in an ambliopic population.

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Purpose: Theta Burst Stimulation can in uence adult neuro-visual response in imbalanced visual pathways, possibly by in uencing cortical excitability. Our objective was to compare suppressive imbalance (SI) and visual acuity (VA) after applying repetitive Transcranial Magnetic Stimulation (TMS) between groups of subjects with normal binocular vision, visual asymmetry and amblyopia.Methods: Thirty -ve volunteers between 19 and 51 years of age, were split into three groups: 6 volunteers with asymmetric VA (group A); 19 amblyopes (group B); and 10 subjects with normal binocular vision (group C). VA and SI of all groups were evaluated before and after a single session of continuous theta-burst stimulation (cTBS) or placebo stimulation over the right occipital cortex.Results: In both groups A and B we found a signi cant VA improvement in the non-dominant eye after cTBS (p=0.04 and p=0.01, respectively). In SI evaluation, group A and group B also revealed a signi cant improvement after the cTBS session (p=0.03 and p=0.01, respectively).Finally, in the group of volunteers with normal binocular vision and for placebo groups A and B, there were no signi cant differences in VA and SI after cTBS.Conclusions: Amblyopic and visually asymmetric individuals improved VA and SI of the non-dominant eye after cTBS when compared to baseline and to placebo stimulation. These enhancements were not found in the group of volunteers with normal binocular vision. We can therefore reasonably assume that cTBS may interfere with the visual system of subjects that present some kind of asymmetry, possibly by improving neuronal imbalances.