Optimal Non-invasive Brain Stimulation for Peripheral Vision

Glaucoma Clinical Trial

Official title: Identify Optimal Non-invasive Brain Stimulation Paradigm for Improving Peripheral Vision

Status Recruiting

Clinical Trial Summary

Glaucoma is a complex disease that can result in progressive vision loss. There are no treatments that restore vision lost to glaucoma. However, recent studies have shown that vision can be improved by non-invasive brain (NIBS) stimulation and visual training. In this study, we aim to compare and find out the optimal non-invasive brain stimulation model (transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS)) for improving peripheral vision in glaucoma patients. The proposed treatment is the application of transcranial electrical stimulation (tES) onto the participant's head, with brain stimulation aimed at the Primary Visual Cortex toward the occipital pole. The investigators hypothesize that the tES will enable higher performance in the reading task and secondary measures due to an increase in the cortical excitability of the stimulated brain cells, and tRNS will generate the greatest acute improvement in peripheral vision than either a-tDCS, tACS, or sham stimulation.

Clinical Trial Description

This study uses a within-subjects, double-blind, placebo-controlled design and will be carried out in Hong Kong (The Hong Kong Polytechnic University).

Participants who will be recruited are 40 glaucoma patients aged 18 to 80, diagnosed with primary open-angle or normal-tension glaucoma with relative scotoma in both eyes. All participants will take part in 4 stimulation sessions (completion of active a-tDCS, tACS, tRNS, and sham stimulation in random order) with at least 48-hour separation between visits to wash out active stimulation effects.

The primary outcome is high-resolution perimetry that will be used to measure the visual field of participants. The secondary outcome is multifocal visual evoked potential (mfVEP) that will be used to measure the electrophysiological changes in the visual cortex.

The study consists of 5 visits:

Visit 1: Eligibility assessment (refer to the inclusion and exclusion criteria).

Visits 2 - 5: Stimulation sessions (completion of active a-tDCS, tACS, tRNS, and sham stimulation in random order) with at least 48-hours separation between visits to wash out active stimulation effects. An established protocol will be used. Briefly, active a-tDCS (2 mA), tACS (2 mA), tRNS (2 mA) or sham a-tDCS will be delivered for 20 minutes. The anodal electrode will be placed at Oz (visual cortex) while the cathodal electrode will be placed on the left cheek to facilitate stimulation of cells corresponding to the para-central retina that are located within the calcarine sulcus. Active stimulation will involve the delivery of 2 mA current continuously, while the fade-in-short-stimulation-fade-out approach will be used for the sham condition, in which the stimulation will be ramped down after 30 seconds of stimulation. Both the participant and experimenter will be masked to the stimulation type.

The average detection accuracy, response time, and functional connectivity will be analyzed using a within-subjects ANOVA with factors of Stimulation type (a-tDCS vs. tACS vs. tRNS vs. sham) and Time (pre and post-stimulation). Significant interactions will be investigated using post-hoc Bonferroni-adjusted paired sample t-tests. A significant interaction between Stimulation type and Time for the primary outcome followed by a significant post-hoc comparison with a p-value <0.05 favoring tRNS would be consistent with our hypothesis. ;

Related Conditions & MeSH terms

• Glaucoma

• NCT number: NCT04846140
• Study type: Interventional
• Source: The Hong Kong Polytechnic University
• Contact: Allen Cheong, PhD
• Phone: 852-27666108
• Email: allen.my.cheong@polyu.edu.hk
• Status: Recruiting
• Phase: N/A
• Start date: November 1, 2021
• Completion date: September 2024