This is a randomized, pilot interventional study in participants with visual field deficit (VFD) caused by cortical lesion. Damage to the primary visual cortex (V1) causes a contra-lesional, homonymous loss of conscious vision termed hemianopsia, the loss of one half of the visual field. The goal of this project is to elaborate and refine a rehabilitation protocol for VFD participants. It is hypothesized that visual restoration training using moving stimuli coupled with noninvasive current stimulation on the visual cortex will promote and speed up recovery of visual abilities within the blind field in VFD participants. Moreover, it is expected that visual recovery positively correlates with reduction of the blind field, as measured with traditional visual perimetry: the Humphrey visual field test or an eye-tracker based visual perimetry implemented in a virtual reality (VR) headset. Finally, although results will vary among participants depending on the extent and severity of the cortical lesion, it is expected that a bigger increase in neural response to moving stimuli in the blind visual field in cortical motion area, for those participants who will show the largest behavioral improvement after training. The overarching goals for the study are as follows: Group 1a will test the basic effects of transcranial random noise stimulation (tRNS) coupled with visual training in stroke cohorts, including (i) both chronic/subacute ischemic and chronic hemorrhagic VFD stroke participants, and (ii) longitudinal testing up to 6 months post-treatment. Group 1b will test the effects of transcranial tRNS coupled with visual training on a Virtual Reality (VR) device in stroke cohorts, including both chronic/subacute ischemic and chronic hemorrhagic VFD stroke participants. Group 2 will examine the effects of tRNS alone, without visual training, also including chronic and subacute VFD stroke participants and longitudinal testing.
18 years of age or older.
Presence of some intact visual cortical areas (other than primary visual cortex) in the damaged brain hemisphere. This assessment will be made from MRI or CT scans of the subject's head, which will be obtained via standard release from their neurologist.
First ever ischemic or hemorrhagic stroke with damage to primary visual cortex, and rendered blind over a portion of their visual field.
Ischemic stroke patients will be either subacute (within 6 months of their stroke) or chronic (more than 6 months)
No evidence of damage to the primary visual cortex.
Visual cortex damage as a result of a subsequent stroke (not primary).
Total cortical blindness, covering both left and right visual fields.
Unable to fixate visual targets precisely or unable to perform the visual training exercises as directed.
Factorial
transcranial random noise stimulation (tRNS)
Devicenoninvasive current stimulation for 20 - 30 minutes stimulation on visual cortex (electrodes on surface of scalp, positioned O1 / O2 on EEG cap). 1mA max amplitude noise stimulation, frequencies from 100 Hz - 640 Hz.
Computer Based Visual Training
BehavioralDynamic visual stimuli are presented on specific locations of the visual field. Participant holds fixation on center of screen during presentation of visual stimuli. Participants will be presented with multiple trials of a motion discrimination task. Training will be performed for 2 weeks (10 consecutive weekdays), 30 minutes each day.
Sham stimulation
Device20-30 minutes sham stimulation on visual cortex. Participants receive identical setup to real stimulation. The device provides a short ramp on period to simulate the feeling of real stimulation at the start but no current is delivered otherwise.
Virtual Reality Based Visual Training
Behavioral• Dynamic visual stimuli are presented on specific locations of the visual field. Participant holds fixation on center point within the VR headset during presentation of visual stimuli. Participants will be presented with multiple trials of a motion discrimination task. Training will be performed for 2 weeks (10 consecutive weekdays), 30 minutes each day.
Visual Motion Discrimination Change
Change in the motion discrimination computer or VR task after training within the blind visual field
Quality of Life Change
Change as assessed by the National Eye Institute 25 Item Visual Function Questionnaire (NEI-VFQ 25). The NEI-VFQ is a vision based questionnaire which evaluates quality of life with respect to vision in everyday life. The NEI-VFQ has multiple sub-scales for different areas of life, such as Near-Vision, General Health, or Ocular Pain. Each scale is scored from 0 to 100 with 100 representing the best possible score (perfect health or ability)
Visual Field Change
Change of the blind area in the visual fields as measured by Humphrey perimetry or an eye-tracker based visual perimetry implemented in a virtual reality (VR) headset.
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