Occipital stroke is associated with homonymous visual field defects (occurring on one side of the visual field). Despite spontaneous recovery, some degree of defect is often permanent. Currently, no treatment exists for such visual field defects.The purpose of this study is to test the efficacy of a type of electrical brain stimulation method, transcranial alternating current stimulation, in reducing these type of visual field defects in their chronic stage.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
50
Transcranial alternating current stimulation (tACS) is administered using DC-Stimulator MC (NeuroConn GmbH, Ilmenau Germany). Stimulation is administered through two 5 cm2 saline-soaked electrodes placed in the Fpz position and on the right arm. Stimulation will consist of short blocks, during which stimulation frequency will be ramped up to 30Hz with maximum current of 1.5mA. Stimulation will be administered for 20 minutes on 10 consecutive weekdays.
Patients in the sham group will undergo the same preparations as the treatment group. This includes using an identical electrode placement and session duration as for the experimental arm. In order to create the effect of phosphenes, one 5Hz current burst per minute will be administered using the individual phosphene threshold of the patient. This is not expected to have therapeutic effects.
Helsinki University Central Hospital
Helsinki, Finland
Improved detection in the visual field defined as the percentage change of the stimulus detection rate in High-resolution perimetry (HRP)
HRP is a computer-based perimetry using a supra-threshold stimulus. It is used to detect residual vision between the absolute defect and seeing field and to monitor subtle changes in perceptual ability. HRP is performed in fixation control using an eye tracker. The primary outcome measure will be the percentage change in HRP detection accuracy between pre-test and post-test measurements.
Time frame: Change between 3-7 days pre-treatment, at 3-7 days post-treatment, and at 2 months post-treatment
The change in extent of visual fields in standard automated perimetry
A secondary outcome measure will be the change in extent of visual fields i.e. mean threshold measured by means of standard automated perimetry.
Time frame: Change between 3-7 days pre-treatment, at 3-7 days post-treatment, and at 2 months post-treatment
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